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Biomedical subjects

D Drake

Publications and source records attributed to D Drake.

69 records · Page 4Linked to original sources
PubMed1985

Nodules are induced on alfalfa roots by Agrobacterium tumefaciens and Rhizobium trifolii containing small segments of the Rhizobium meliloti nodulation region.

Regions of the Rhizobium meliloti nodulation genes from the symbiotic plasmid were transferred to Agrobacterium tumefaciens and Rhizobium trifolii by conjugation. The A. tumefaciens and R. trifolii transconjugants were unable to elicit curling of alfalfa root hairs, but were able to induce nodule development at a low frequency. These were judged to be genuine nodules on the basis of cytological and developmental criteria. Like genuine alfalfa nodules, the nodules were initiated from divisions of the inner root cortical cells. They developed a distally positioned meristem and several peripheral vascular bundles. An endodermis separated the inner tissues of the nodule from the surrounding cortex. No infection threads were found to penetrate either root hairs or the nodule cells. Bacteria were found only in intercellular spaces. Thus, alfalfa nodules induced by A. tumefaciens and R. trifolii transconjugants carrying small nodulation clones of R. meliloti were completely devoid of intracellular bacteria. When these strains were inoculated onto white clover roots, small nodule-like protrusions developed that, when examined cytologically, were found to more closely resemble roots than nodules. Although the meristem was broadened and lacked a root cap, the protrusions had a central vascular bundle and other rootlike features. Our results suggest that morphogenesis of alfalfa root nodules can be uncoupled from infection thread formation. The genes encoded in the 8.7-kilobase nodulation fragment are sufficient in A. tumefaciens or R. trifolii backgrounds for nodule morphogenesis.

Conjugation, Genetic↗
PubMed1985

Pseudomonas pili. Studies on antigenic determinants and mammalian cell receptors.

P. aeruginosa PAK pili are thin 5.2 nm diameter filaments containing a single 15-kd polypeptide subunit which is 144 amino acid residues in length. Studies on pili binding to a variety of synthetic sugars representing many di- tri- and tetra-saccharide structures found in mammalian glycoproteins and glycolipids failed to reveal any significant binding activity. On the other hand, a wide spectrum of binding activities was observed when a variety of structural proteins and enzymes were used as binding substrates. Of 30 proteins tested, phosphorylase b, pyruvate kinase and aldolase showed highest pilus binding activity. It was concluded that the PAK pilus receptor is probably a polypeptide rather than an oligosaccharide. Using arginine-specific cleavage to produce four large peptides, several proteases to produce subfragments of the large peptides, and antipilus rabbit antiserum, PAK pilin was found to contain four antigenic determinants. Epitopes near the NH2- and COOH-termini were only weakly immunogenic, whereas two epitopes near the center of the pilus protein titrated about 85% of the antipilus antibodies. Cleavage of the pilus protein into smaller peptides resulted in marked decreases in the affinity of antigenic peptides for their specific antibodies, suggesting that the immunodominant epitopes of PAK pilin are conformation-specific.

Amino Acid Sequence↗
PubMed1981

Neutralizing capacity and cost effectiveness of antacids.

The prescribing physician is faced with a wide choice of antacid preparations. To provide a guide, we tested the commonly available antacids, both liquid and tablet, for their acid-neutralizing capacity. We calculated the cost effectiveness of antacids and tabulated the cost of 1 month of therapy. The acid-neutralizing capacity and cost effectiveness of liquid antacids are generally better than tablet antacids. The most effective liquid antacids, which are composed of either aluminum and magnesium hydroxide mixtures or calcium carbonate, vary in buffering capacity from 3 to 4.2 meq/mL of antacid and range in monthly cost of therapy from $35 to $74. In contrast, the five least effective liquid antacids vary in acid-neutralizing capacity from 0.3 to 2.3 meq/mL of antacid and in monthly cost of therapy from $78 to $498. Because the monthly cost of therapy is influenced primarily by the acid-neutralizing capacity of the antacid, a high-potency antacid should be prescribed. The taste and sodium content of the antacids should also be taken into account by the prescribing physician.

Aluminum Hydroxide↗
PubMed1981

Treatment of radial neuropathy associated with fractures of the humerus.

Twenty-four humeral-shaft fractures with associated radial-nerve injuries in twenty-three patients with adequate follow-up were seen over a fifteen-year period. Initial treatment was closed in all but one patient, in whom débridement of an open fracture revealed a lacerated radial nerve. All patients had complete return of radial-nerve function. Two of the twenty-four nerve lesions were treated by delayed operation: one at fourteen weeks for entrapment in fracture callus, and the other at six weeks for repair of the aforementioned lacerated radial nerve. Thus, only 8 per cent of the patients required exploration of the nerve, all of whom did well after delayed repair. We recommend careful observation for return of nerve function and exploration at three and a half to four months after injury if there is still no clinical or electromyographic evidence of recovery at that time.

Adolescent↗
PubMed1977

Maternal language to prelinguistic infants: syntactic aspects.

Maternal speech to children has been shown to vary by age and language ability of the children. Previous studies have usually involved children over 1 year of age. In this study maternal speech to male and female 4-, 6-, and 8-month-old infants was recorded in the laboratory. Mothers used shorter utterances to 8-month-olds than to 4- or 6-month-olds, presumably in response to the infant's changing level of comprehension. Mothers used more sentences with subjects, verbs, or objects deleted to 8-month-olds and more complex sentences to 4-month-olds.

Female↗
PubMed1976

Mutual visual regard during mother-infant play.

Mutual visual regard was observed in 48 mother-infant dyads during a 6-min. play session. Infant-mother dyads containing 4 mo. -olds displayed significantly more mutual visual regard than dyads containing 6- or 8-mo.-olds. In addition, the more time infants spent in face-to-face interaction with mother, the more smiling they engaged in. No sex difference were observed.

Age Factors↗
PubMedDate not supplied

Management of esophageal atresia.

A total of 303 infants with esophageal atresia and/or tracheoesophageal fistula were treated over 10 years (1980-1989). The overall survival rate was 86.5%. Associated anomalies were identified in 51.8% of patients, the most common being cardiac malformations which affected 24.4% of infants and was responsible for the majority of deaths. The dramatic increase in survival of infants with esophageal atresia in the past half century is due to improvements in pre- and postoperative management, meticulous operative technique to reduce anastomotic complications, and aggressive treatment of associated congenital anomalies.

Anastomosis, Surgical↗
PubMedDate not supplied

Effects of four anticaries agents on lesion depth progression in an in vitro caries model.

PURPOSE: This study compares four chemotherapeutic regimens used for inhibiting carious lesion progression: silver nitrate (AgNO3); silver fluoride/stannous fluoride (AgF/SnF2); silver diammine fluoride (SDF); and chlorhexidine (CHX). METHODS: For this study, a bacterial model system containing Mutans streptococci (MS) and Lactobacilli casei (L) was used to generate carious lesions on 85 extracted sound permanent third molars which were randomly assigned to four test groups and one control group. At week two, the four treatment regimens were applied to the lesions (one treatment per test group). RESULTS: Six weeks later, lesions treated with a single AgF/SnF2 or AgNO3 application demonstrated 29% and 19% less lesion progression, respectively, than did the control group (P < 0.05). SDF and CHX did not differ significantly from the control. CONCLUSION: AgF/SnF2 and AgNO3 may be useful in slowing down carious lesion depth progression.

Analysis of Variance↗
PubMedDate not supplied

Efficacy of denture cleansing agents in an in vitro bacteria-yeast colonization model.

The purpose of this investigation was to develop a new, in vitro bacteria-yeast denture colonization model. Candida albicans and Streptococcus mutans, organisms associated with denture stomatitis, reproducibly colonized denture blanks in high numbers. Both Efferdent and Super-Strength Polident were able to substantially reduce or eliminate colonizing S mutans. In sharp contrast, however, no significant decreases in adherent C albicans were observed with either denture soaking agent.

Candida albicans↗