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Biomedical subjects

B Smith

Publications and source records attributed to B Smith.

At least 325 records · Page 18Linked to original sources
PubMed1988

A highly polymorphic locus very tightly linked to the Huntington's disease gene.

The genetic defect in Huntington's disease (HD), an inherited neuropsychiatric disorder of unknown etiology, has not been defined. The discovery of linkage between HD and the DNA marker D4S10(G8) raised the possibility of isolating the disease gene on the basis of its chromosomal location, in addition to providing a limited presymptomatic test for the late onset disorder. But it has been difficult to isolate other DNA markers nearer to the HD gene, and this has hampered attempts to identify the disease locus and limited the applicability and accuracy of predictive testing. Recently, several new DNA markers from the region of the genome near the HD gene have been isolated using a directed cloning strategy. We describe here the characterization of one of these new markers, D4S95, a highly polymorphic locus which displays no recombination with the HD gene in the families tested. The high degree of polymorphism at this locus and its proximity to the HD gene make it extremely useful for predictive testing and as a new starting point for attempts to clone the disease gene.

Alleles↗
PubMed1988

Two methods for measuring the non-randomness of chromosome abnormalities.

Applying conventional statistical techniques to cytogenetic data usually faces the problem of working with small numbers and many classes. We describe two techniques, one based on a binomial test procedure, the other on Monte Carlo simulations, aimed at studying the non-randomness of chromosomal aberrations. Both techniques were used to study the distribution of breakpoints involved in variant Philadelphia translocations in chronic myeloid leukaemia. The results showed that 28 bands were non-randomly rearranged (P less than or equal to 0.05). Furthermore, the probabilities calculated from the binomial test procedure were close to those calculated from the Monte Carlo simulations.

Chromosome Aberrations↗
PubMed1988

Radiotherapy of periocular basal cell carcinomas: recurrence rates and treatment with special attention to the medical canthus.

Basal cell carcinomas of the eyelids, especially those in the medial canthal area, may cause extensive local destruction. Recurrent tumours are more aggressive and become progressively more difficult to treat; this is especially true for postirradiated recurrent, medial canthal, basal cell carcinomas. Tumours in this area should thus be treated by a technique which allows tissue sampling in order to gauge the adequacy of the treatment, with the goal being complete extirpation of the tumour. Excision monitored by frozen section control or Mohs' surgery is our recommendation based on a retrospective analyses of 631 eyelid basal cell carcinomas, half of which were primary tumours and half recurrent.

Adult↗
PubMed1988

Dexamethasone attenuates reversal of hypertension in one-kidney, one-clip rats.

This study examines the effect of dexamethasone (Dex), a phospholipase A2 inhibitor, on the reversal of 1-kidney, 1-clip (1K,1C) hypertension and the synthesis of phospholipase A2-dependent products. Male Sprague-Dawley 1K,1C hypertensive rats [blood pressure (BP) greater than 190 mmHg] were allocated to three groups: two groups were given daily oral doses of Dex (0.142 mg/kg in water) for 72 h, whereas the third group was given water only (controls). One of the Dex-treated groups was then sham unclipped (n = 9), while the other Dex-treated group (n = 8) and the control group (n = 8) were unclipped. Dex attenuated the BP fall in the unclipped (223 +/- 8-148 +/- 9 mmHg) compared with the control unclipped (226 +/- 9-114 +/- 5 mmHg) animals (P less than 0.005). Aortic 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) was reduced in unclipped Dex-treated rats (13.4 +/- 1.2 ng/mg) compared with unclipped control rats (16.3 +/- 1.4 ng/mg; P less than 0.05) but was higher than in the sham-unclipped Dex group (11.5 +/- 1.2 ng/mg; P less than 0.05). Serum thromboxane B2 (TxB2) in the unclipped Dex-treated group was lower than in the unclipped control rats (P less than 0.05) but higher than in sham-unclipped rats (P less than 0.05). Dex significantly increased urinary prostaglandin E2 (PGE2) excretion, whereas urinary 6-keto-PGF1 alpha was unaltered. After unclipping, both urinary PGE2 and 6-keto-PGF1 alpha increased significantly, although there was no obvious difference between Dex-treated and control animals. These findings demonstrate opposite effects of Dex on renal compared with extrarenal prostanoid synthesis and support the hypothesis that attenuation of aortic 6-keto-PGF1 alpha synthesis may be responsible for the smaller fall in BP after unclipping in Dex-treated rats.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

A polymorphic DNA marker that represents a conserved expressed sequence in the region of the Huntington disease gene.

A polymorphic marker (D4S62) that is genetically closely linked to D4S10 and is in the region of the gene for Huntington disease is described. A four-allele polymorphism is detected when HincII-digested DNA is hybridized with D4S62. D4S62 maps, by Southern blot analysis using somatic-cell hybrids, to 4p16.1 closer to the centromere than does D4S10. The use of the polymorphisms detected by D4S62 increases the informativeness of markers close to the gene for Huntington disease and will be useful for preclinical diagnosis. D4S62 detects transcripts of approximately 6,000 nucleotides in rat, mouse, and monkey liver and brain. This represents the first demonstration of conserved expressed sequences close to the gene for Huntington disease.

Alleles↗
PubMed1988

Isolation of DNA markers in the direction of the Huntington disease gene from the G8 locus.

To facilitate identification of additional DNA markers near and on opposite sides of the Huntington disease (HD) gene, we developed a panel of somatic-cell hybrids that allows accurate subregional mapping of DNA fragments in the distal portion of 4p. By means of the hybrid-cell mapping panel and a library of DNA fragments enriched for sequences from the terminal one-third of the short arm of chromosome 4, 105 DNA fragments were mapped to six different physical regions within 4p15-4pter. Four polymorphic DNA fragments of particular interest were identified, at least three of which are distal to the HD-linked D4S10 (G8) locus, a region of 4p previously devoid of DNA markers. Since the HD gene has also recently been shown to be distal to G8, these newly identified DNA markers are in the direction of the HD gene from G8, and one or more of them may be on the opposite side of HD from G8.

Animals↗
PubMed1988

Complications of blepharoplasty.

Various involutional eyelid changes, such as fine rhytids, dynamic laugh lines in the lateral canthal area, secondary malar bags, and dermal pigmentation are not effectively treated by a blepharoplasty. Preoperative discussions are important to ensure that adequate expectations are held. Too often, a patient is informed that fine rhytids and dermal pigmentation can be successfully treated with lid surgery alone. The importance of the preoperative interview in determining patient expectations cannot be minimized. Preoperative ophthalmic and periocular examination is essential to identify any pre-existing pathology. Even though the surgical approach is adapted to the individual needs of each patient, the most meticulous of surgeons is predetermined to encounter his or her share of complications. There is a fine line between a "complication" and a common, but unwanted, sequela of surgery. Patients, overwhelmingly, do have some widening of their palpebral fissures, even following conservative surgery. Unfortunately, this occasionally creates ocular irritation or gross discomfort in allergic or borderline dry eyed patients. Lower eyelid bowing is so common even in the face of minimal skin resection that we do not consider it a "complication" if it does not produce a functional problem. It is humbling for all surgeons to review their blepharoplasty problems and helpful to recognize that, statistically, we are all due to face these events eventually.

Eye Hemorrhage↗
PubMed1987

Equilibrium binding of derivatives of the carcinogen, benzo(a)pyrene, to DNA. Thermodynamic analysis.

The physical binding of polycyclic aromatic hydrocarbon derivatives which are ultimate carcinogens to DNA may play a role in the formation of covalent DNA adducts by these compounds or in the detoxification of the compounds via DNA-catalyzed hydrolysis. Previous studies of DNA-binding interactions of derivatives of benzo(a)pyrene (BP) have been confined to low r values (r - ligands bound/base pair). We have now applied the Scatchard formalism (as modified to include neighbor exclusion) to the spectrophotometric determination of the binding of two derivatives of BP, trans - 9,10 - dihydroxydihydro - BP and 7r,8t - dihydroxy-9t,10t-oxy-7,8, 9,10-tetrahydro-BP, to double-stranded DNA at reasonably high r values. Exclusion parameters, binding constants, and thermodynamic parameters are all within the ranges found for other intercalants. Although these ligands are uncharged, the binding exhibits significant ionic strength dependence which can be rationalized (partially) by polyelectrolyte theory. Using the measured ionic strength dependence, a thermodynamic association constant, independent of ionic interactions, can be calculated which is very close to the calculated thermodynamic association constants for ethidium and proflavine.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1987

Role of metallothionein in detoxification and tolerance to transition metals.

Animal tolerance to the transition metals cadmium and zinc is hereditary. The evolution to a high level of resistance can be accelerated through mutation and selective pressure. We have studied inbred strains of mice and mutants of Chinese hamster ovary cells resistant to cadmium to further these understandings. Results with whole animals show that the difference in the rate and level of metallothionein accumulation is at most twofold between sensitive and resistant strains. However, with cadmium resistant CHO mutant cells, there is an over 60 fold increase in metallothionein and its mRNA upon induction. These mutants show over 60 fold amplification in metallothionein genes. These results offer a direct contrast in the correlation between elevation of metal resistance and increases in metallothionein between two genetic systems.

Animals↗
PubMed1987

Efficacy of surgical treatment for paralytic ectropion.

Paralytic ectropion can be corrected with numerous procedures. Advocates of particular procedures have previously been unable to quote statistical rates of success for each procedure over significant lengths of time. This study reviews over 200 cases of paralytic ectropion, representing the spectrum of seventh nerve disease seen at an eye and ear specialty hospital and a general medical facility. Of all eyelid implantation devices 93 to 95% failed to work or needed reoperation by 3 years postoperatively. Soft tissue surgery without prosthetic implants or exoplants provided 60% success after a 3-year follow-up. Eyelid elevation or tightening coupled with surgery for facial reanimation produced a higher rate of success at 3 years (83%). An overwhelming number of patients (62%) complained of some degree of epiphora after any or all procedures. Based on these findings, soft tissue surgery without prosthetic implants or exoplants has a higher rate of success.

Ectropion↗
PubMed1987

Fatal pancreatitis presenting with subcutaneous fat necrosis. Evidence that lipase and amylase alone do not induce lipocyte necrosis.

We report a case of fatal pancreatitis heralded by the presence of cutaneous panniculitis without abdominal pain or other stigmata of the disease. Although cutaneous fat necrosis has been associated with pancreatitis, it is unusual as the presenting complaint of this relatively common disease. In vitro evidence suggests that human pancreatic amylase or lipase alone is not responsible for the observed panniculitis.

Acute Disease↗
PubMed1987

Pitfalls of autogenous lipodermal implantation to the orbit.

Autogenous kinetic lipodermal implantation in the orbit is an effective postenucleation procedure that gives optimal socket volume, motility, and cosmesis. The major complication of autogenous lipodermal implantation is graft atrophy. Other minor complications are infection, hair retention, conjunctival cysts, wound dehiscence, and suture granuloma. We presented a systematic description of the technique emphasizing prevention of complications by proper selection of patients, meticulously performed surgery, and appropriate postoperative management. In particular, attention should be paid to atraumatic dissection of the socket-respecting surgical anatomy, hemostasis, identification and placement of sutures in the extraocular muscles, atraumatic and aseptic manipulation of the graft, and proper anastomosis of the graft to the recipient bed.

Adipose Tissue↗
PubMed1987

Experience with tarsal suspension as a factor in lower lid blepharoplasty.

The bowed lower eyelid, with scleral show, is a common but untoward result following blepharoplasty with even minimal skin excision. A number of conditions, unrecognized preoperatively, can predispose a patient to scleral show. These include eyelid laxity with or without atrophic orbicularis muscle tone, lax canthal tendons, hypoplastic malar eminences, unrecognized Graves' ophthalmopathy, unilateral high myopia, or the secondary blepharoplasty. Suspension of the tarsus of the lower eyelid, concomitant with or following blepharoplasty, can straighten bowed lids and provide 2 to 3 mm of elevation, if desired. A classification of patients likely to develop scleral show is presented along with a revised technique of tarsal suspension.

Adolescent↗