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Biomedical subjects

J W Little

Publications and source records attributed to J W Little.

At least 73 records · Page 4Linked to original sources
PubMed1991

Increasing CD8+ T lymphocytes predict subsequent development of intraoral lesions among individuals in the early stages of infection by the human immunodeficiency virus.

Determining the progression of human immunodeficiency virus (HIV) type 1 infection based on cellular and clinical markers has become increasingly important. Although a number of studies have shown a relationship between the presence of certain oral lesions and progression to AIDS, few data exist regarding the association with T lymphocyte counts. In this study, the question of whether intraoral lesions preceded or were the consequences of changes in T lymphocyte counts was examined. A total of 116 HIV-infected patients participating in two randomized double-blind placebo-controlled trials of zidovudine at the University of Minnesota AIDS Clinical Trials Unit (ACTU) were enrolled in a prospective dental study. Patients were examined for the presence of hairy leukoplakia, candidiasis, herpes simplex, herpes zoster, aphthae, atypical gingivitis, HIV-associated periodontitis, and necrotizing ulcerative gingivitis, as well as other oral lesions, every 3 months for a maximum of four examinations over a 1-year period. T lymphocyte counts before and after each patient's oral examination were obtained. No significant differences were found at examination 1 for differences in gender, race, age, education, tobacco smoking status, ethanol consumption habits, duration in ACTU drug protocol, duration in dental study protocol, or mean T lymphocyte counts between individuals with or without oral lesions at any time in the dental study.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗
PubMed1991

Prosthetic implants: risk of infection from transient dental bacteremias.

This paper examines the issue of risk for infection from transient dental bacteremias in patients with implanted prosthetic devices. Guidelines are available to dentists from the American Heart Association concerning patients with prosthetic heart valves, but other national medical organizations have thus far not provided recommendations regarding patients with other prosthetic devices. The author reviews the literature and offers recommendations for the dental management of these patients.

Dental Care↗
PubMed1991

Methyl prednisolone in double-lumen gel-saline submuscular mammary prostheses: a double-blind, prospective, controlled clinical trial.

At the time of immediate breast reconstruction with submuscular implants, 76 consecutive patients (89 breasts) were randomized into two groups. One received a gel-saline, double-lumen implant with 40 cc of saline added to the outer lumen, while the other received the same implant plus 40 cc of saline and 16 mg methyl prednisolone (40 mg%). Patients were followed for a minimum of 3 years. The groups, which were matched for patient age and implant size, were evaluated at 3, 12, 24, and 36 months for capsular contracture, steroid atrophy, and other complications. With completion of the double-blind study, the patients with submuscular gel-saline implants with only saline added had an overall capsular contracture rate of 38 percent at 3 months, 38 percent at 12 months, and 44 percent at 24 and 36 months. Those with methyl prednisolone had an overall capsular contracture rate of 14 percent at 3 months, and this remained unchanged through the end of the study. The rates of all other complications were comparable. Methyl prednisolone in a dose of 16 mg in 40 cc saline (concentration 40 mg%), when used in the outer lumen of a double-lumen gel-saline implant in a submuscular pocket, is both safe and efficacious in reducing the risk of capsular contracture for a minimum of 3 years in patients undergoing immediate breast reconstruction with submuscular mammary implants.

Adult↗
PubMed1991

Immobilization impairs recovery after spinal cord injury.

The effect of immobilization on motor recovery was studied in adult rats after subtotal spinal cord section. Anesthetized rats underwent three-quarter section of the cord, sparing the left lateral funiculus. After surgery, half the rats were placed in immobilization tubes for three to four weeks; the others were allowed free mobility. Hindlimb motor function was graded at various times in the two groups. In contrast to the marked recovery observed in mobile animals, the immobilized rats with similar cord lesions showed no significant motor recovery during the period of immobilization. Immobilized rats without cord lesions showed minimal transient deficits. In conclusion, hindlimb activity appears to be a necessary condition for motor recovery after subtotal spinal cord injury.

Animals↗
PubMed1990

Reaction of LexA repressor with diisopropyl fluorophosphate. A test of the serine protease model.

The LexA repressor of Escherichia coli modulates the expression of the SOS regulon. In the presence of DNA damaging agents in vivo, the 202-amino acid LexA repressor is inactivated by specific RecA-mediated cleavage of the Ala-84/Gly-85 peptide bond. In vitro. LexA cleavage requires activated RecA at neutral pH, and proceeds spontaneously at high pH in an intramolecular reaction termed autodigestion. A model has been proposed for the mechanism of autodigestion in which serine 119 serves as the reactive nucleophile that attacks the Ala-84/Gly-85 peptide bond in a manner analogous to a serine protease, while uncharged lysine 156 activates the serine 119 hydroxyl group. In this work, we have tested this model by examining the effect of the serine protease inhibitor diisopropyl fluorophosphate (DFP) on autodigestion. We found that DFP inhibited autodigestion and that serine 119 was the only serine residue to react with DFP. We also examined [3H]DFP incorporation by a number of cleavage-impaired LexA mutant proteins and found that mutations in the proposed active site, but not in the cleavage site, significantly reduced the rate of [3H]DFP incorporation. Finally, we showed that the purified carboxyl-terminal domain, which contains the proposed catalytic residues, incorporated [3H]DFP at a rate indistinguishable from the intact protein. These data further support our current model for the mechanism of autodigestion and the organization of LexA.

Amino Acid Sequence↗
PubMed1990

Saturation mutagenesis of specific codons: elimination of molecules with stop codons from mixed pools of DNA.

In saturation mutagenesis of a protein, pools of DNA molecules are made containing a mixture of codons at a specific position. In cases where genetic methods allow screens or selections for altered function, a background of nonsense mutations can complicate genetic analysis of the resulting mutations. Methods are proposed for elimination of those molecules containing stop codons at the target codon from the pool, and for identifying positions to which these methods may be applied. Application of these methods should ensure that all changes are missense mutations, thereby simplifying genetic analysis.

Amino Acid Sequence↗
PubMed1990

Dental patient reaction to electrocardiogram screening.

Ninety-one patients receiving routine dental treatment at the University of Minnesota School of Dentistry participated in an electrocardiogram screening study. The purpose of the study was to evaluate patient reaction to electrocardiogram screening in a dental school clinic. The vast majority of patients indicated the test was easy and did not intrude on the dental appointment. Most of the patients reported that the test was a valuable service and should be available in the dental office. None of the patients indicated that the tests should not be performed in the dental office. Few patients expressed any significant concern or anxiety about the test either before or after it was completed. Twenty-six percent (24/91) of the patients were found to have a cardiac arrhythmia; however, most of these were nonserious arrhythmias (18/24) and would not have had an impact on planned dental procedures. Six patients were identified with arrhythmias that required medical referral before dental treatment was started.

Adolescent↗
PubMed1990

The development of penicillin-resistant oral streptococci after repeated penicillin prophylaxis.

Oral streptococci may cause infective endocarditis in patients with susceptible cardiac disease after dental treatment. Multiple dental visits, each preceded by penicillin prophylaxis, may result in the unwanted development of resistant oral streptococci. This study was undertaken to determine whether resistant oral streptococci would develop after the repeated use of penicillin prophylaxis in healthy adults. Plaque samples were collected from 20 subjects on each Monday for 5 successive weeks. Each subject was administered 2 gm penicillin V followed by 1 gm 6 hours later (standard prophylaxis regimen of the American Heart Association), on three successive Mondays (weeks 2, 3, and 4). The total cultivable oral streptococci and penicillin-resistant oral streptococci were determined for each plaque sample, and representative colonies of resistant streptococci were speciated. During the study, there was a significant increase in the number of subjects who harbored penicillin-resistant oral streptococci. However, with the exception of one subject who had resistant streptococci throughout the study, the number of resistant strains represented only 0.0003% to 0.41% of the total cultivable oral streptococci.

Adult↗
PubMed1990

Effect of abx, bx and pbx mutations on expression of homeotic genes in Drosophila larvae.

We have examined the patterns of expression of the homeotic gene Ubx in imaginal discs of Drosophila larvae carrying mutations in the abx, bx and pbx regulatory domains. In haltere discs, all five bx insertion mutations examined led to a general reduction in Ubx expression in the anterior compartment; for a given allele, the strength of the adult cuticle phenotype correlated with the degree of Ubx reduction. Deletions mapping near or overlapping the sites of bx insertions, including three abx alleles and the bx34e-prv(bx-prv) allele, showed greatly reduced Ubx expression in parts of the anterior compartment of the haltere disc; however, anterior patches of strong Ubx expression often remained, in highly variable patterns. As expected, the pbx1 mutation led to reduced Ubx expression in the posterior compartment of the haltere disc; surprisingly, pbx1 also led to altered expression of the en protein near the compartment border in the central region of the disc. In the metathoracic leg, all the bx alleles caused extreme reduction in Ubx expression in the anterior regions, with no allele-specific differences. In contrast, abx and bx-prv alleles resulted in patchy anterior reductions in third leg discs. In the larval central nervous system, abx but not bx alleles affected Ubx expression; the bx-prv deletion gave a wild-type phenotype, but it could not fully complement abx mutations. In the posterior wing disc, the bx-prv allele, and to a much lesser extent the bx34e chromosome from which it arose, led to ectopic expression of Ubx. Unlike other grain-of-function mutations in the BX-C, this phenotype appeared to be partially recessive to wild type. Finally, we asked whether the ppx transformation, which results from early lack of Ubx+ function in the mesothorax and is seen in abx animals, is due to ectopic Scr expression. Some mesothoracic leg and wing discs from abx2 larvae displayed ectopic expression of Scr, which was variable in extent but always confined to the posterior compartment.

Alleles↗
PubMed1990

Motor-evoked potentials reflect spinal cord function in post-traumatic syringomyelia.

The purpose of this study was to examine electrophysiologic abnormalities, including motor-evoked potentials, in a patient with post-traumatic syringomyelia before and after syringopleural shunting. A patient with C5 quadriplegia presented with pain, ascending sensory loss, and new weakness in the left upper extremity two yr after spinal cord injury. MRI revealed a syrinx extending from C2 to T12. We measured central motor conduction times (CMCTs) to the biceps, median F-wave latencies, needle electromyography and motor nerve conduction studies. Six days before surgery, CMCTs were 9.0 ms on the left and 7.8 ms on the right (normal less than 8.0), median F-waves were absent on the left and needle EMG revealed evidence of denervation in the left biceps. Fifteen days after syringopleural shunting at the T7 level, CMCTs had dropped to 6.9 ms on the left and 4.6 ms on the right; the left median F-wave reappeared with a normal latency. Repeat MRI revealed the syrinx to be smaller in diameter. These results suggest that CMCTs measured from magnetic stimulation of the motor cortex may be useful in the diagnosis of post-traumatic syringomyelia, as well as for following such patients postoperatively.

Adult↗
PubMed1990

Guidelines in concentric mastopexy.

The scope and technique of concentric mastopexy remain unclear and controversial. In our hands, the procedure has application for mild nipple ptosis, glandular ptosis, and areola asymmetry, as well as the tuberous breast. Early disappointment has changed to increasing satisfaction as we have gained confidence in predicting our results based on the identification of three simple principles of concentric mastopexy. The first and most important, which states Doutside less than or equal to Doriginal + (Doriginal - Dinside), requires that the outer concentric circle must be drawn not to exceed the original areola diameter by more than the original areola diameter exceeds the inner concentric circle diameter. The second principle, Doutside less than or equal to 2 X Dinside, recommends that the outer circle diameter be drawn not to exceed twice that of the inner circle, to prevent poor scarring or over flattening of the breast. The third principle, Dfinal = 1/2(Doutside + Dinside), allows prediction of the final areola size as the average of the diameters of the inner and outer concentric circles. These three principles allow excision of a maximum amount of areola and periareola skin without the side effect of poor scars, dilated areola, or misshapened breasts. Applying these three principles to concentric mastopexy with or without augmentation mammaplasty, one may confidently correct a wide variety of deformities, producing more symmetrical, attractive breasts with areolae of a predictable size.

Breast↗
PubMed1990

Variations on the temporoparietal fascial flap.

An improved understanding of the vascular supply of the layers of the temporal fossa has increased the potential of this region for new and ingenious reconstructive techniques. Separate and independently vascularized layers of this region include hair-bearing scalp, glabrous skin, tempororoparietal fascia (and galea aponeurotica), temporalis muscle and fascia, and pericranium. Island flaps of glabrous skin and scalp provided esthetically appropriate tissue to cover a variety of defects. The malleable bulk of the subcutaneous fascial layers were combined with skin grafts to restore thin lining, and used as a vascularized bed for cartilage grafts in otherwise unsatisfactory recipient sites. Illustrative cases from our 5-year clinical experience are presented to demonstrate various combinations of the temporoparietal fascial pedicle with tissues from the temporal region to reconstruct the eyebrows, eyelids, orbits, cheeks, and lips.

Adolescent↗
PubMed1989

Autodigestion and RecA-dependent cleavage of Ind- mutant LexA proteins.

The LexA repressor of Escherichia coli undergoes a specific cleavage reaction in vivo, an event that leads to derepression of the SOS regulon and requires an activated form of RecA protein. In vitro, cleavage requires RecA at neutral pH; at alkaline pH, a spontaneous cleavage reaction termed autodigestion takes place. Both autodigestion and RecA-mediated cleavage cut the same bond, and are observed for the same set of substrates, suggesting that RecA acts indirectly to stimulate LexA self-cleavage at neutral pH, perhaps binding to LexA and acting as an allosteric effector. We previously isolated a set of lexA(Ind-) mutants that are deficient in in vivo RecA-mediated cleavage but retain significant repressor function. Here, we describe the in vitro cleavage of purified mutant proteins. All of those tested were deficient in both cleavage reactions. Although most of them were equally deficient in both reactions, some were more deficient in one reaction than the other. Several mutant proteins appeared to have defects in binding to RecA. Autodigestion of all but one of the poorly cleavable mutant proteins reached a maximum rate at pH around 10, as does wild-type LexA. The exception was KR156, which changed Lys156, a residue previously implicated in the mechanism of cleavage, to Arg, another basic residue: for this protein, the rate of autodigestion increased with pH at values above 11. RecA-mediated cleavage of KR156 was 1% the wild-type rate at pH 7, but increased with increasing pH to a plateau at pH 9.5, where the rate was 40% the wild-type rate. In contrast, an essentially constant rate was observed for wild-type LexA over the pH range 6 to 11. We suggest, first, that deprotonation of Arg156 and, by inference, Lys156 in the wild-type protein, is required for both autodigestion and RecA-mediated cleavage: and second, that RecA acts to reduce the pKa of Lys156, allowing efficient cleavage of wild-type repressor under physiological conditions.

Bacterial Proteins↗