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Biomedical subjects

C M Lawrence

Publications and source records attributed to C M Lawrence.

At least 55 records · Page 3Linked to original sources
PubMed1996

The relevance and effect of amalgam replacement in subjects with oral lichenoid reactions.

In this study we examined the prevalence of mercury hypersensitivity in patients with oral lichenoid reactions (OLR) and the effect of amalgam replacement in subjects with amalgams adjacent to OLR irrespective of their mercury sensitivity status. One hundred and ninety-seven patients with oral problems were examined: 109 with OLR, 22 with oral and generalized lichen planus, and 66 with other oral diagnoses, including aphthous ulcers and orofacial granulomatosis. Nineteen per cent of patients with OLR reacted to mercury on patch testing, significantly more than in those with generalized lichen planus (0%) and in those with other oral diagnoses (3%). Twenty-two patients with OLR and adjacent amalgams had amalgam replacement and, in 16 of 17 mercury-positive subjects and three of four mercury-negative subjects, the OLR resolved after amalgam removal. In conclusion, we found a significantly increased prevalence of mercury hypersensitivity in patients with localized OLR in comparison to subjects with other oral problems. Amalgam replacement resulted in resolution of OLR in the majority of patients with amalgams adjacent to OLR irrespective of their mercury sensitivity status.

Adult↗
PubMed1995

Crystal structure of Pseudomonas mevalonii HMG-CoA reductase at 3.0 angstrom resolution.

The rate-limiting step in cholesterol biosynthesis in mammals is catalyzed by 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a four-electron oxidoreductase that converts HMG-CoA to mevalonate. The crystal structure of HMG-CoA reductase from Pseudomonas mevalonii was determined at 3.0 angstrom resolution by multiple isomorphous replacement. The structure reveals a tightly bound dimer that brings together at the subunit interface the conserved residues implicated in substrate binding and catalysis. These dimers are packed about a threefold crystallographic axis, forming a hexamer with 23 point group symmetry. Difference Fourier studies reveal the binding sites for the substrates HMG-CoA and reduced or oxidized nicotinamide adenine dinucleotide [NAD(H)] and demonstrate that the active sites are at the dimer interfaces. The HMG-CoA is bound by a domain with an unusual fold, consisting of a central alpha helix surrounded by a triangular set of walls of beta sheets and alpha helices. The NAD(H) is bound by a domain characterized by an antiparallel beta structure that defines a class of dinucleotide-binding domains.

Acyl Coenzyme A↗
PubMed1995

Crystallization of HMG-CoA reductase from Pseudomonas mevalonii.

Crystals of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase from Pseudomonas mevalonii have been grown by vapor diffusion in hanging drops at pH 6.7 using ammonium sulfate as the precipitant. Serial dilution seeding and manipulation of glycerol concentration were both used to obtain crystals larger than 1.0 mm. The crystals are cubic, space group I4(1)32, with a = 229.4 A. A V(m) value of 2.71 A(3) Da(-l) indicates 96 molecules per unit cell with two molecules in the asymmetric unit. These crystals diffract to 2.8 A with conventional X-ray sources, and beyond 2.4 A with synchrotron radiation.

Journal Article↗
PubMed1995

Resolution of lichen planus following removal of amalgam restorations in patients with proven allergy to mercury salts: a pilot study.

Thirteen patients with symptomatic oral lichen planus had been shown by patch testing to be allergic to ammoniated mercuric chloride. Replacement of amalgam restorations in these patients effected an improvement in all but one case. In some cases the resolution of symptoms was dramatic following the replacement of one or two fillings. The authors feel that the removal of all amalgam fillings need not be necessary except in the most intractable case.

Adult↗
PubMed1995

Shave excision of benign papular naevocytic naevi.

Patients frequently request removal of benign papular naevi for cosmetic or functional reasons. Shave excision plus electrocautery is probably the most widely used method of removal, but this method is said to result in retained hair or pigment if deeply pigmented or hairy naevi are treated. In a prospective study, 82 benign papular naevi of all types were treated by shave excision using hot-wire electrocautery for haemostasis. Details of the naevi were accurately recorded before treatment and reassessment of shave sites carried out at 6-8 months. At review, a scar was visible at only 63% (52/82) of shave sites and all of these were cosmetically acceptable. Only 27% (15/55) of the initially pigmented naevi retained pigment and only 24% (5/21) of the initially hairy naevi regrew hair. Shave excision and electrocautery of benign naevi, including hairy and deeply pigmented ones, produce excellent cosmetic results. The patient must be warned that there is a potential risk of a scar or pigment remaining after shave excision of any naevus and for hair regrowth after shave excision of hairy naevi.

Adolescent↗
PubMed1995

Comparison of wound closure by means of dog ear repair and elliptical excision.

BACKGROUND: Elliptical excision is a standard method of skin tumor removal. The technique commits the operator to the direction and length of wound closure before lesion excision and hence before the shape and size of the resulting defect is known. OBJECTIVE: This study was designed to compare the predicted results of elliptical excision with those achieved after tumor excision and dog ear repair. METHODS: Fifty-one patients with benign and malignant skin tumors were prospectively studied. Each lesion was examined and an optimal ellipse designed and marked on the skin. Only the lesion and the required margin of adjacent skin were excised before the defect was closed in an optimal direction. Dog ears were removed if appropriate. Precise measurements were made at each step. RESULTS: Twenty-eight percent of wounds could be closed with a flat sutured wound without the need for dog ear repair, 38% required one dog ear repair, and 34% two. Overall, the sutured wound length was 21% shorter and the wound direction different from the predicted ellipse in 45% of cases. CONCLUSION: Excision with dog ear repair results in significantly shorter and potentially better oriented wounds than those achieved by elliptical excision. For excision and closure of skin tumors this technique should be considered as the method of choice.

Adolescent↗
PubMed1995

Relation between size of skin excision, wound, and specimen.

BACKGROUND: Skin wounds differ in shape and size compared with the planned excision, and skin shrinks after excision and fixation. OBJECTIVE: This study was designed to quantify and to analyze the differences between the size and shape of the planned excision, wound, and specimen. METHODS: Eighty-six patients with 93 benign or malignant skin tumors were prospectively studied. Length and width measurements were made of the lesion, planned surgical excision, postexcision wound, and prefixation and postfixation specimens. The results were analyzed to identify the effects of patient age and sex, and lesion type and site. RESULTS: Wound size was larger than planned excision size in 90% of wounds, and this effect was greatest in young patients and at trunk and limb sites. Excision and fixation caused the specimens to shrink so that the postfixation area was on average 48% of the planned excision area; benign tumors shrank more than malignant tumors. CONCLUSION: Significant differences among planned excision, wound, and specimen sizes are influenced by patient age and by lesion site and type. These results demonstrate that wound size is not equivalent to tumor size, a conclusion often made in Mohs surgery. Furthermore, assessment of tumor clearance margins from fixed tissue does not reflect in vivo clearance margins.

Adolescent↗
PubMed1995

Prognostic value of Ki67 antigen expression in basal cell carcinomas.

Recurrence of basal cell carcinoma (BCC) following treatment is a common event and long-term follow-up of all patients presenting with a primary BCC has been recommended. Proliferation indices have been recognized as important prognostic factors in several tumour types in a variety of cancer systems, being significantly elevated in more aggressive lesions. We have examined 51 BCCs (17 non-recurrent tumours [group 1], 17 original tumours which later recurred [group 2-O], and the corresponding 17 recurrent specimens [group 2-R]) for Ki67 antigen expression, a proliferation-associated antigen using immunohistochemistry with the monoclonal antibody MIB1. There was a significant increase in the percentage positive for MIB1 in the Group 2-O as compared with the group 1 BCCs (P < 0.05). p53 protein expression, as assessed by immunohistochemistry with the monoclonal antibody DO7, was similar in each group. These results show that Ki67 antigen expression differs between BCCs which later recur and BCCs that do not recur.

Aged↗
PubMed1995

The effect of ketanserin on healing of fresh surgical wounds.

This study was designed to investigate the effect of topical ketanserin, a selective S2-serotonin antagonist, on wound healing and contraction in surgical wounds allowed to heal by second intention. Thirty-five patients applied placebo or 2% ketanserin gel, double-blind, to head and neck wounds resulting from skin tumour excision, and allowed to heal by second intention. Healing rate was assessed from the change in the square root of wound area, and in 11 patients wound contraction was assessed by the change in the area delineated by wound margin tattoo marks. There were no significant differences in any of the measurements made between the ketanserin- and placebo gel-treated patients. Wound healing was significantly faster in large wounds. Wound contraction was greatest in the early stages of healing, and accounted for 53% of healing. We conclude that, on normally vascularized skin, ketanserin gel has no significant effect on wound healing rate.

Adult↗
PubMed1994

Crystallization and preliminary X-ray analysis of the low molecular weight phosphotyrosyl protein phosphatase from bovine heart.

Two crystal forms of bovine heart phosphotyrosyl protein phosphatase (BHPTP) have been examined by X-ray analysis. One crystal form grows as long rods with triclinic crystal symmetry and diffracts to 3 A resolution. The diffraction pattern of this form of the crystal shows twinning about a major axis. A second crystal form of BHPTP grows as flat trapezoidal prisms with monoclinic symmetry C2, and unit cell parameters a = 95.3 A, b = 43.3 A, c = 41.2 A and beta = 113.5 degrees. The unit cell dimensions indicate that there is one 18 kDa molecule per asymmetric unit. These crystals diffract to at least 2.2 A resolution and are resistant to decay in the X-ray beam.

Animals↗
PubMed1994

Follicular keratoses at amputation sites.

We describe two patients with painful follicular keratoses at lower limb amputation sites. Subsequent examination of 31 amputees revealed evidence of keratoses in four of 28 patients with lower limb stumps. Two of the four affected subjects experienced stump pain exacerbated by weight-bearing. This problem is not well documented. Local treatment measures may be ineffective. Painful stump follicular keratoses may be a cause of significant morbidity in lower limb amputees, and may be the result of an ill-fitting prosthesis.

Adult↗
PubMed1993

Mohs surgery of basal cell carcinoma--a critical review.

Mohs surgery for basal cell carcinoma (BCC) of the skin attempts to ensure complete tumour removal by histological examination of the entire excision margin and further excision of involved sites. Advocates recommend its use in recurrent or incompletely excised tumours, poorly defined, histologically aggressive or large primary tumours and BCCs situated at high risk or cosmetically important sites. The claimed advantages over other surgical therapies are that it provides a better chance of cure and since less normal tissue is removed the simpler surgical repair ensures a superior cosmetic result. This review examines the published evidence that supports the enthusiasm for the use of Mohs surgery in the treatment of BCC, contrasting cure rates and cosmetic outcome with results achieved by attempted single complete excision and examines the 2 principles upon which Mohs surgery is based, namely that BCCs spread by contiguous growth and that all tumour cells have to be destroyed to achieve a cure.

Basal Cell Carcinoma↗
PubMed1993

The use of a digitizer to measure area in dermatology.

The accuracy and reproducibility of area measurements made with a computerized digitizer were studied. Known areas were measured varying the way in which the system was operated, altering the characteristics of the shapes being measured and varying the ways in which the image on the computer screen was formed. Accuracy and reproducibility were dependent on all these factors; altering the operating technique caused the mean measured area to vary from 76% to 124% of the actual area, with the greatest inaccuracies being produced by altering the computer screen image. The accuracy and reproducibility of results obtained using a digitizer are critically dependent on the way in which it is used.

Analog-Digital Conversion↗