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Biomedical subjects

W Lawson

Publications and source records attributed to W Lawson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Phospholipases and melatonin signal transduction in the ovine pars tuberalis.

The potential role of phospholipases in mediating melatonin-dependent inhibition of adenylyl cyclase was investigated in pars tuberalis (PT) cultures. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated the release of choline metabolites and increased the transphosphatidylation reaction. The calcium ionophore A23187 stimulated the release of arachidonic acid from cultures. These observations demonstrate phospholipase A and D activities within PT. Phosphatidic acid inhibited forskolin-stimulated production of cyclic AMP both in PT cells and in membrane preparations. This indicates that melatonin could inhibit adenylyl cyclase by increasing phosphatidic acid levels through activation of cellular phospholipases. Melatonin did not stimulate the release of arachidonic acid or choline from PT cultures, nor did it increase intracellular levels of hydrophobic second messengers or stimulate transphosphatidylation. Therefore melatonin does not stimulate phospholipase A and D pathways in PT cells. However, these pathways are present in the PT and their activation could potentially modulate the cellular actions of melatonin.

Adenylyl Cyclases↗
PubMed1994

p72, a marker protein for melatonin action in ovine pars tuberalis cells: its regulation by protein kinase A and protein kinase C and differential secretion relative to prolactin.

The function of the pars tuberalis as a mediator of the action of melatonin remains elusive. As a direct method of assessing the potential role of secretory proteins, ovine pars tuberalis cells have been cultured and radiolabelled with 35S-methionine, and the accumulation of specific radioactive products in the medium, measured after separation by SDS-PAGE and fluorography. The synthesis and secretion of a number of labelled proteins are increased by forskolin (1 microM) and inhibited dose dependently by melatonin (IC50, 300 pM), although consistently a 72-kD protein (p72), is the most intensely labelled of these. Thus, 72 acts as a useful marker of cellular activity for melatonin, whereas prolactin (p23) provides a melatonin non-responsive marker in ovine pars tuberalis cell cultures. The synthesis and secretion of p72 and other melatonin-sensitive proteins is regulated through the cyclic AMP/protein kinase A second-messenger pathway, as analogues of cyclic AMP mimic the action of forskolin, yet 1,9-dideoxyforskolin, a forskolin analogue that is not active on adenylate cyclase, has no effect. However, the phorbol ester, phorbol-12,13-myristate acetate, also regulates the synthesis and secretion of the same profile of proteins as forskolin indicating a potential role for protein kinase C, which occurs through an independent rather than a synergistic pathway. The differential effects of nocadazole (1 microM) and extracellular calcium depletion upon p72 and prolactin secretion indicates that p72 is secreted by a calcium and microtubule independent pathway, in contrast to prolactin. These observations in conjunction with the absence of dense-core storage vesicles in melatonin-responsive cells of the ovine PT are consistent with constitutive secretion of p72 from the latter and regulated secretion of prolactin from melatonin non-responsive cells. Using immunoprecipitation de novo synthesis and secretion of either LH or LH-like proteins from ovine pars tuberalis cells could not be detected under the conditions used. The absence of 125I-(Des-Gly10[D-Ala6]-LHRH-ethylamide) binding over most, but not all, of the ovine pars tuberalis supports the contention that the majority of the cells of the ovine pars tuberalis are not gonadotrophs. These results provide further support for the unique function for the pars tuberalis.

Animals↗
PubMed1994

Inflammatory pseudotumor of the maxillary sinus: CT and MR findings in six cases.

OBJECTIVE: Inflammatory pseudotumor is a chronic inflammatory lesion of unknown origin. The purpose of this study was to analyze the CT and MR findings in six cases of inflammatory pseudotumor of the maxillary sinus in order to determine if there were any imaging findings that distinguish this lesion from the more common type of pseudotumor that occurs in the orbit. MATERIALS AND METHODS: Six patients with pseudotumor of the maxillary sinus were identified retrospectively. The diagnosis was based on biopsy specimens. Their CT scans and MR images were studied by two radiologists to identify specifically the presence of soft-tissue disease and the presence and type of any bone involvement. RESULTS: CT and MR images showed some degree of involvement of the bony wall in all cases. All patients had a soft-tissue mass with mild enhancement on CT scans and intermediate signal intensity on both T1- and T2-weighted MR images. CONCLUSION: Our experience shows that inflammatory pseudotumor of the maxillary sinus causes bone changes on CT and MR images, findings that mimic a malignant tumor. Bone involvement appears to be more common in pseudotumor of the maxillary antrum than in its orbital counterpart.

Adolescent↗
PubMed1994

The varied presentations of papillary thyroid carcinoma cervical nodal disease: CT and MR findings.

PURPOSE: To review the varied presentations of metastatic cervical lymph node disease in patients with papillary thyroid carcinoma. METHODS: Thirteen cases were retrospectively collected and their clinical, imaging, surgical, and pathologic material was reviewed. In the cases reviewed there was no clinical or imaging evidence of a primary thyroid mass. RESULTS: On CT, metastatic nodes can have multiple discrete calcifications, appear as benign cysts or hyperplastic or hypervascular nodes, or have areas of high attenuation which reflect intranodal hemorrhage and/or high concentrations of thyroglobulin. On MR, the nodes can have low to intermediate T1- and high T2-weighted signal intensities or high T1- and T2-weighted signal intensities, the latter reflecting primarily a high thyroglobulin content. CONCLUSION: If any of these varied appearances of cervical lymph nodes are identified on CT or MR, especially in a woman between 20 and 40 years of age, the radiologist should suspect the diagnosis of papillary thyroid carcinoma, even in the absence of a thyroid mass.

Adult↗
PubMed1993

Infrared thermography in the detection and management of coronary artery disease.

Infrared thermography was used to measure and map precordial skin temperature in 60 patients undergoing elective coronary angiography; 9 patients were normal and 51 had coronary artery disease (CAD). Thermograms were graded by quartile area (zero to 4 plus) and magnitude of thermal asymmetry (recorded as degrees celsius). The presence, mean area and degree of thermal asymmetry were significantly greater in patients with CAD. Twenty-two patients subsequently underwent successful revascularization with angioplasty with a highly significant decrease in the presence, magnitude and degree of thermal asymmetry. The results demonstrate that CAD is associated with precordial thermal asymmetry. The area and magnitude of thermal asymmetry is greater in patients with CAD than in control subjects without angiographically significant CAD. Successful revascularization changed the asymmetric precordial pattern to a more symmetric one. Infrared thermography is a promising technique for the detection of CAD before and after revascularization.

Adult↗
PubMed1993

The male facelift. An analysis of 115 cases.

Based on the anatomic differences in female and male cervicofacial skin, a retrospective study of 115 male facelifts was undertaken to identify those factors that contributed to a satisfactory esthetic result and the avoidance of complications. Incision modifications are reported, as well as the need for ancillary procedures (in 37% of the patients) to obtain facial rejuvenation. An increased incidence of hematomas (9.6%) was noted.

Cicatrix, Hypertrophic↗
PubMed1993

Correlates of patterns of substance abuse among patients with schizophrenia.

OBJECTIVE: Most previous research on substance abuse among patients with schizophrenia has not considered the types of substances abused or the confounding influences of polysubstance abuse. The authors' goals were to identify patterns of substance abuse among a sample of subjects with schizophrenia and to determine demographic and clinical correlates of these patterns. METHODS: Subjects with schizophrenia were identified from the Epidemiologic Catchment Area study data base, which also provided information on the types of substances abused and on selected demographic and clinical characteristics. Latent class analysis was used to group subjects based on their patterns of substance abuse. Logistic regression was used to identify demographic and clinical correlates of the patterns. RESULTS: Three latent classes based on patterns of substance abuse were identified: no substance abuse, abuse of alcohol and cannabis, and polysubstance abuse. Subjects with either of the two patterns of substance abuse were more likely to be younger and male and to have depressive symptoms. CONCLUSIONS: The results do not support a link between abuse of specific substances and specific clinical symptoms but do suggest a general link between substance abuse and affective disturbance among schizophrenic patients.

Alcoholism↗
PubMed1993

Prolonged exposure to melatonin leads to time-dependent sensitization of adenylate cyclase and down-regulates melatonin receptors in pars tuberalis cells from ovine pituitary.

In photoperiodic mammals, seasonal cycles of growth and reproduction are cued by changes in the duration of the nocturnal profile of secretion of the pineal hormone melatonin. To investigate the likely mode of action of this hormone on target tissues, the effect of prolonged treatment with melatonin on the sensitivity of the adenylate cyclase (AC) system was examined in primary cultures of ovine pars tuberalis (PT) cells. When cells were exposed to melatonin (100 pM or 1 microM) for 16 h, and the hormone was then removed by a series of washes, basal production of cAMP was elevated over that observed in cells not treated with melatonin. Moreover, the rate of accumulation of cAMP after stimulation with forskolin (1 microM) was markedly enhanced in cells previously treated with melatonin compared to that in untreated controls. This sensitization by melatonin of the basal and forskolin-stimulated responses developed gradually and was half-maximal after approximately 8 h of exposure. There was no significant difference between the sensitizing effects of the two melatonin concentrations used. Treatment with melatonin for 24 h reduced the total amount of specific [125I]iodomelatonin binding in PT cell membranes by 30-50%. However, over the same period there was no reduction in the ability of a maximal (1 microM) concentration of melatonin to inhibit forskolin-stimulated cAMP production, indicating the presence of an excess capacity of melatonin receptors in cultured PT cells. Nevertheless, treatment with melatonin for 16 h did result in a 10-fold increase in the IC50 for the inhibition by melatonin of forskolin-stimulated cAMP production. The enhancement of cAMP production after prolonged treatment with melatonin was not masked by the inclusion of isobutylmethylxanthine (1 mM) during the subsequent challenge with forskolin, suggesting that sensitization was not due to a reduction in the activity of cAMP-phosphodiesterase. In control cells, aluminium fluoride caused an inhibition of forskolin-stimulated cAMP production. Prolonged treatment with melatonin abolished the inhibitory effect of aluminium fluoride, suggesting that treatment with melatonin caused a shift in the net balance between the G-protein-mediated stimulatory and inhibitory influences on the AC system. The sensitization of AC was not blocked by the inclusion of cycloheximide (10 micrograms/ml) during prolonged exposure to melatonin, suggesting that de novo protein synthesis is not a requirement for this effect of the hormone. These results constitute the first demonstration of an independent action of melatonin on ovine PT cells that is dependent upon the duration of the endocrine stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1993

Psychological characteristics related to cocaine use during pregnancy: a postpartum assessment.

This study assessed four psychological factors that have been suggested by previous research to be highly correlated with drug use. Twenty-one postpartum urban African-American women served as the research participants. At parturition, 10 infants tested positive for cocaine and 11 did not. Measures of depression (Beck Depression Index), anxiety (Spielberger Trait Anxiety Inventory), anger/self-control (Self-Analysis Questionnaire), and sociopathy (California Personality Inventory subscale) were obtained from the mothers within 6 weeks of delivery. Women who gave birth to cocaine-positive infants were significantly more depressed and had significantly higher sociopathy scores than their cocaine-negative counterparts. No differences with respect to anxiety and anger were obtained. The implications of these findings, as well as the potential adverse effects of cocaine use during pregnancy, are discussed.

Adolescent↗
PubMed1993

Fungal infections of the nose and paranasal sinuses. Part I.

This article details the incidence, etiology, classification, and radiographic findings of fungal infections. Major infections discussed include aspergillosis, mucormycosis, blastomycosis, candidiasis, chromblastomycosis, coccidioidomycosis, histoplasmosis, paracoccidioidomycosis, and rhinosporidiosis.

Humans↗
PubMed1993

Fungal infections of the nose and paranasal sinuses. Part II.

This article, the second of two, examines the following infections in detail: phaeohyphomycosis, bipolaris infections, Exserohilim infections, multiple-fungal infections, allergic dematiaceous sinusitis, Pseudallescheria infections, sporothricosis, basidoiomycetous infections, Paecilomyces infections, penicilliosis, Cryptococcus infections, and others.

Humans↗
PubMed1992

The superior trapezius myocutaneous flap in head and neck reconstruction.

The superior trapezius myocutaneous flap, based on the paraspinous perforating branches of the intercostal vessels, is generally not a first-line choice for reconstruction of head and neck defects. However, after wound breakdown following radical neck dissection and radiation therapy, the superior trapezius flap is extremely reliable for coverage of exposed major neck vessels. The flap was used in 30 patients undergoing lateral neck reconstruction. All 30 patients had undergone prior neck dissection and all but two had undergone prior radiation therapy. There were no flap failures. The superior trapezius flap is unique among other regional myocutaneous flaps presently in use in that it has a superiorly based pedicle, which reduces the problem of gravitational pull on the suture lines of severely unfavorable recipient beds. Another advantage of using the denervated muscle of this flap is that it imposes no additional functional loss. The deficiencies of this flap are primarily related to its limited arc of rotation, thereby precluding its use when resurfacing defects that extend beyond the midline of the neck. The reliability of the superior trapezius flap after neck dissection can be explained by the angiosome concept. Based on that concept, previous ligation of the transverse cervical vessels during a neck dissection serves to simultaneously stage this flap, thereby improving its reliability and potential surface area available.

Adult↗
PubMed1992

The combined sensate radical forearm and iliac crest free flaps for reconstruction of significant glossectomy-mandibulectomy defects.

The loss of motor and sensory function of the tongue following ablative surgery has a devastating effect on oral function. At the present time, there is no way to restore lost tongue musculature following partial glossectomy. The use of sensate cutaneous flaps has been shown to restore sensory feedback to reconstructed areas of the oral cavity. No single composite flap supplies a sensate soft-tissue component together with an osseous component of sufficient bone stock for functional mastication. In this article, the combination of the radial forearm free flap with the iliac crest osteocutaneous or osteomyocutaneous free flap is reported. The radial forearm free flap was used to resurface the resected portion of the tongue to provide maximum mobility and sensation. The lingual nerve was the recipient nerve for anastomosis to the antebrachial cutaneous nerves in all but one case. The iliac bone was used to reconstruct the mandible, with the iliac skin paddle or the internal oblique muscle used to reconstruct the neoridge. This combination of flaps was used in 10 patients. There was one flap failure due to vascular kinking from "piggybacking" the iliac crest to the distal end of the radial forearm flap. As a result, the use of two separate sets of recipient vessels is now advocated. Although a single composite free flap offers an excellent form of oromandibular reconstruction in most cases, it has been shown that oral function deteriorates when large areas of anesthesia are present in the oral cavity. We believe that this combination of two free flaps offers an opportunity for superior function in select patients with significant glossectomy and/or large mucosal defects.

Anastomosis, Surgical↗
PubMed1991

The lower trapezius island musculocutaneous flap revisited. Report of 45 cases and a unifying concept of the vascular supply.

The lower trapezius island musculocutaneous flap is valuable in head and neck reconstruction. It offers thin, pliable tissue and a long arc of rotation to reach virtually any defect in the head and neck. Recent reports have shown unacceptably high rates of failure and have questioned the reliability of the vascularity. We report our experience with 45 reconstructions using the lower trapezius island musculocutaneous flap. The literature is reviewed and the vascular anatomy is described in detail. The concept of angiosomes is applied to the trapezius muscle to help explain the reasons for flap failure and to provide guidelines for flap design and harvest.

Face↗