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Biomedical subjects

L Allen

Publications and source records attributed to L Allen.

At least 109 records · Page 6Linked to original sources
PubMed1990

The role of tissue expanders in an anophthalmic animal model.

A study of orbital bony expansion using a custom tissue expander was performed in the anophthalmic cat model. Twelve 6-week-old kittens underwent right unilateral enucleations. Six kittens had immediate insertion of a tissue expander into the orbit. The remaining six served as controls. Every 2 weeks 0.5 cc saline was injected into the expander to a maximum of 5 cc. External horizontal and vertical orbital dimensions were obtained by palpation technique weekly. All animals had preoperative and study conclusion head CT scans with three-dimensional reconstructions performed. Dry skull preparations were done at the study conclusion at 24 weeks. Results demonstrated that tissue expanders were successful in maintaining normal orbital growth and size relative to the contralateral control orbit. The animals with enucleation only had an average difference in vertical and horizontal orbital measurements of -27 and -13 percent when compared with the contralateral normal orbit. In contrast, the enucleation and tissue-expansion animals had vertical and horizontal measurements of +4 and +2 percent (p less than 0.05) when compared with the contralateral orbit. Head CT scans with three-dimensional reconstructions demonstrated normal orbital geometry and volume for the animals with tissue expanders, whereas animals with enucleation only had small hypoplastic orbits. In conclusion, orbital tissue expanders offer a promising new technique in the treatment of anophthalmos.

Animals↗
PubMed1989

Localization of a human brain sodium channel gene (SCN2A) to chromosome 2.

A DNA probe derived from a human genomic library has been used to localize on human chromosomes a gene coding for the alpha-subunit of the brain type II sodium channel (SCN2A). Hybridization of the probe to Southern blots made with DNAs from a rodent-human somatic cell hybrid panel indicates localization to the long arm of human chromosome 2. In situ hybridization to metaphase chromosomes confirms this assignment and indicates regional localization to 2q21-q33. The probe also reveals a frequent two-allele HaeIII RFLP.

Animals↗
PubMed1989

Phosphorescence maxima and triplet state lifetimes of NAD+ and epsilon-NAD+ in ternary complexes with horse liver alcohol dehydrogenase.

This paper describes the phosphorescence emission and decay times of NAD+ and its fluorescent etheno derivative, epsilon-NAD+, in the pyrazole ternary complex with horse liver alcohol dehydrogenase (ADH). We show that the epsilon-NAD+ triplet state, as well as the tryptophan triplet state, can be utilized to monitor the coenzyme-enzyme interaction. The decays of NAD+ and AMP are single exponential, and the lifetimes are the same within experimental error. The phosphorescence lifetimes, evaluated as single exponentials, are slightly shorter in epsilon-NAD+ than they are in epsilon-AMP. Whereas the decay of epsilon-AMP was adequately fit by a single exponential with a time constant of very close to 0.5 s, it was necessary to fit the decay of epsilon-NAD+ to a double exponential. Ternary complexes with NAD+ excited at 297 nm exhibit decay kinetics nearly identical to those of ADH by itself. On the other hand, when excitation of the epsilon-NAD+ ternary complex is provided at 313 nm, where there is very little absorption by either tryptophan residue, the decay law of the ternary complex is similar to that of epsilon-NAD+ in solution. Our results demonstrate that NAD+ and epsilon-NAD+ quench tryptophan phosphorescence in ADH. Normalizing the phosphorescence intensity to the 0-0 vibronic band assigned to Trp-15 (blue-edge), we calculate a 21% decrease in the phosphorescence associated with Trp-314 at stoichiometric saturation of the coenzyme binding sites with NAD+ in the ternary complex. When the active sites are saturated with epsilon-NAD+, the relative phosphorescence due to Trp-314 decreases by 63%.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Dehydrogenase↗
PubMed1989

The human dopamine D2 receptor gene is located on chromosome 11 at q22-q23 and identifies a TaqI RFLP.

Human dopaminergic neurons are involved in the control of hormone secretion, voluntary movement, and emotional behavior. Mediating these effects are the dopamine D1 and D2 receptors. These macromolecules belong to a large family of related sequences known as the G protein-coupled receptors. The D2 receptors have been of special interest because they bind, with high affinity and specificity, many of the commonly prescribed antipsychotic drugs. We previously isolated a full-length cDNA clone of the rat D2 receptor. When a chromosome mapping panel was probed with the rat D2 receptor cDNA a 15-kb EcoRI restriction fragment was identified and localized to human chromosome 11. The rat cDNA was also used to clone a human genomic fragment, lambda hD2G1, which contains the last coding exon of the D2 receptor gene (DRD2) and 16.5 kb of 3' flanking sequence. Hybridization of lambda hD2G1 to a chromosome 11 regional mapping panel localized DRD2 to 11q. In situ hybridization of lambda hD2G1 to metaphase chromosomes refined this assignment to the q22-q23 junction of chromosome 11. A search for RFLPs associated with D2DR identified a frequent two-allele TaqI RFLP.

Chromosome Mapping↗
PubMed1988

Plasma levels of highly sulphated glycosaminoglycans are raised in patients with chronic myeloid leukaemia.

A study of absolute basophil counts and plasma levels of highly sulphated glycosaminoglycans in 30 peripheral blood samples from 21 patients with different leukaemias was performed. This revealed significantly raised levels of both plasma highly sulphated glycosaminoglycans and basophils in those patients with chronic myeloid leukaemia, as compared to those with other types of leukaemia and 35 normal controls. A strong correlation (r = 0.83) was observed between the levels of highly sulphated glycosaminoglycans and basophil counts in the group as a whole, supporting a direct relationship between the two. The elevated plasma levels of highly sulphated glycosaminoglycans may contribute to the bleeding tendency reported in some patients with chronic myeloid leukaemia.

Adult↗
PubMed1988

Diltiazem, nifedipine, and their combination in patients with stable angina pectoris: effects on angina, exercise tolerance, and the ambulatory electrocardiographic ST segment.

The efficacy and safety of oral nifedipine and diltiazem were compared in 20 patients with stable angina pectoris with use of a placebo run-in, randomized, double-blind titration to maximal effect crossover protocol. The effects of treatment withdrawal were also analyzed. All patients received placebo for 2 weeks and were then randomly assigned to receive either diltiazem or nifedipine. A 2 week drug titration phase in which patients received either diltiazem (180 to 360 mg/day) or nifedipine (30 to 120 mg/day) in three divided doses was followed by a 1 week maintenance phase. Patients then received placebo for 1 to 2 weeks, followed by crossover to the other treatment regimen and a second placebo washout period of 1 week. Patients (n = 13) who remained symptomatic on both diltiazem and nifedipine during the monotherapy periods entered a 3 week combination treatment phase, followed by a final 1 week placebo washout period. Frequency of angina, nitroglycerin consumption, exercise tolerance (Naughton protocol), and frequency of daily episodes of ST segment deviations on the electrocardiogram (1 mm of ST segment depression persisting for at least 1 min with and without chest pain) on an ambulatory electrocardiographic monitor were assessed during the baseline placebo, active monotherapy, placebo withdrawal, and combination treatment phases. Plasma drug levels were also measured. Compared with initial placebo values, the frequency of angina and the amount of nitroglycerin treatment were reduced by both diltiazem (p less than .001) and nifedipine (p less than .02). Diltiazem was more effective than nifedipine in reducing angina (p less than .02). Exercise duration increased with both drugs (p less than .0001). Diltiazem was significantly better than nifedipine in reducing the episodes of ST segment depression on the ambulatory monitor (p less than .01). Diltiazem reduced the resting heart rate (p less than .01); both drugs reduced the resting blood pressure and rate-pressure product. Overall, combination therapy was more effective in patients who did not maximally respond to diltiazem or nifedipine alone with respect to anginal and exercise variables and in reducing blood pressure at rest and during exercise. Plasma drug levels could not predict an individual patient's treatment response. Diltiazem may increase nifedipine drug levels when the drugs are combined. Fewer side effects were observed with diltiazem than nifedipine; the most side effects were seen with combination treatment. There were no apparent withdrawal effects observed with either treatment regimen.(ABSTRACT TRUNCATED AT 400 WORDS)

Angina Pectoris↗
PubMed1987

A preliminary report on the Universal Implant.

Extrusion and time-consuming surgical techniques required of implantation have been the major criticisms of quasi-integrated implants such as the Iowa Implant. With these concerns in mind, the Universal Implant (Oculo-Plastik, Montreal) has been designed to offer the motility advantages seen with quasi-integrated implants and the ease of placement of a sphere. The Universal Implant incorporates most of the advantages seen in the Iowa Implant and other quasi-integrated implants. In addition, the Universal Implant (1) utilizes a faster surgical technique for implantation; (2) avoids cleaning the muscles; (3) has lower, more rounded, smaller mounds that should decrease the late extrusion rate; (4) can be used as an enucleation implant, evisceration implant, or secondary implant; and (5) has a greater girth and larger radius of the posterior surface that helps support orbital fat and tissues, resulting in a more natural superior sulcus. Considering that the Iowa Implant is presently not available, the Universal Implant should be used by those surgeons who were pleased with the former implant and should be considered as a reasonable alternative to other enucleation implants.

Equipment Design↗
PubMed1987

Orchiectomy versus long-acting D-Trp-6-LHRH in advanced prostatic cancer.

One hundred and four patients were randomised for the study. Fifty-five were entered into the D-Trp-6-LHRH group and 49 into the orchiectomy group. All pre-treatment patient characteristics were similar and testosterone levels at 1 month or later were in the castrate range in both groups. Forty-six patients (83%) in the D-Trp-6-LHRH group and 40 (82%) in the orchiectomy group had a partial remission or stable disease at 3 months or later. There was no significant difference between the groups for response or survival. Three patients in the D-Trp-6-LHRH group had a disease "flare" in the first 10 days of treatment. The flare symptoms resolved by the end of 4 to 8 weeks. The incidence of flushing, decreased libido and impotence was similar in both groups. Although there was less psychological morbidity in the D-Trp-6-LHRH group the difference did not reach statistical significance. Our results indicate that long-acting D-Trp-6-LHRH offers a safe and highly effective alternative to orchiectomy.

Clinical Trials as Topic↗
PubMed1986

Metal ion requirements and other aspects of the reaction catalyzed by M1 RNA, the RNA subunit of ribonuclease P from Escherichia coli.

M1 RNA, the RNA subunit of ribonuclease P from Escherichia coli, can under certain conditions catalytically cleave precursors to tRNA in the absence of C5, the protein moiety of RNase P. M1 RNA itself is not cleaved during the reaction, nor does it form any covalent bonds with its substrate. Only magnesium and, to a lesser extent, manganese ions can function at the catalytic center of M1 RNA. Several other ions either inhibit the binding of magnesium ion at the active site or function as structural counterions. The reaction rate of cleavage of precursors to tRNAs by M1 RNA is enhanced in the presence of poly-(ethylene glycol) or 2-methyl-2,4-pentanediol. Many aspects of the reaction catalyzed by M1 RNA are compatible with a mechanism in which phosphodiester bond cleavage is mediated by metal ion.

Binding Sites↗
PubMed1986

Interstitial deletion of (17)(p11.2p11.2) in nine patients.

We describe a new and distinct syndrome involving an interstitial deletion of short arm of chromosome 17 in nine unrelated patients (six males; three females) ranging in age from 3 months to 65 years. In eight patients, a deletion of a portion of band 17p11.2 was associated with a striking similar phenotype including brachycephaly, midface hypoplasia, prognathism, hoarse voice, and speech delay with or without hearing loss, psychomotor and growth retardation, and behavior problems. The one patient with a complete deletion of band 17p11.2 was more severely affected with facial malformations, cleft palate, and major anomalies of cardiac, skeletal, and genitourinary systems; the patient died at age 6 months. Careful cytogenetic analysis including high-resolution techniques will be important for the further identification of patients with this previously unrecognized deletion syndrome.

Abnormalities, Multiple↗
PubMed1986

De novo partial duplication of 17p [dup(17)(p12----p11.2)]: clinical report.

Duplication of band p11.2 and a small proximal portion of band p12 of chromosome 17 was noted in an infant with unusual facial appearance and left calcaneovalgus deformity. Developmental delay was documented over time. Only one other similar case has been found in the literature, but deletion of the same region is known in nine recently described cases [Smith et al, 1986]. This suggests that abnormalities of this small region of 17p are relatively common and only recently detectable with modern high-resolution techniques.

Calcaneus↗