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Biomedical subjects

D J Beech

Publications and source records attributed to D J Beech.

At least 19 recordsLinked to original sources
PubMed2002

Prevention of a hypoxic Ca(2+)(i) response by SERCA inhibitors in cerebral arterioles.

1. The aim of the study was to investigate the mechanism of a novel effect of hypoxia on intracellular Ca(2+) signalling in rabbit cerebral arteriolar smooth muscle cells, an effect that was resistant to the L-type Ca(2+) channel antagonist methoxyverapamil (D600). 2.[Ca(2+)](i) of smooth muscle cells in intact arteriolar fragments was measured using the Ca(2+)-indicator dye fura-PE3. Hypoxia (PO(2) 10 - 20 mmHg) lowered basal [Ca(2+)](i) but did not inhibit Ca(2+) entry pathways measured by Mn(2+)-quenching of fura-PE3. 3. The effect of hypoxia was completely prevented by thapsigargin or cyclopiazonic acid, selective inhibitors of sarcoplasmic reticulum Ca(2+) ATPase (SERCA). Since these inhibitors do not block Ca(2+) extrusion or uptake via the plasma membrane, the data indicate that the effect of hypoxia depends on a functional sarcoplasmic reticulum. 4. Because actions of nitric oxide (NO) on vascular smooth muscle are also prevented by SERCA inhibitors it was explored whether the effect of hypoxia occurred via modulation of endogenous NO release. Residual NOS-I and NOS-III were detected by immunostaining, and there were NO-dependent effects of NOS inhibitors on Ca(2+)(i)-signalling. Nevertheless, inhibition of endogenous NO production did not prevent the effect of hypoxia on [Ca(2+)](i). 5. The experiments reveal a novel nitric oxide-independent effect of hypoxia that is prevented by SERCA inhibitors.

Animals↗
PubMed2002

Potassium channel KV alpha1 subunit expression and function in human detrusor muscle.

PURPOSE: We determined whether voltage gated K+ (KV) channels are expressed and functional in human detrusor smooth muscle MATERIALS AND METHODS: Information on KV channels was obtained using electrophysiological patch clamp, immunofluorescence, Western blot and isometric tension recording techniques RESULTS: Patch clamp recordings from detrusor cells revealed a Ca2+ independent K+ current that was activated by depolarization in a voltage range near the resting potential of detrusor smooth muscle. The current was inhibited by 3,4-diaminopyridine, a blocker of KV channels. Antibodies targeted to KValpha1 subunits revealed KV1.3 and KV1.6 expression in whole bladder tissue samples and specifically in detrusor smooth muscle cells. New specific blockers of KValpha1 channel currents (correolide and recombinant agitoxin-2) had a myogenic effect, characterized by increased amplitude of spontaneous contractions without an effect on the frequency of contractions or on resting baseline tension. CONCLUSIONS: KValpha1 subunits are expressed and functionally important in human detrusor muscle.

Animals↗
PubMed2001

Expression and function of native potassium channel [K(V)alpha1] subunits in terminal arterioles of rabbit.

1. In this study we investigated the expression and function of the K(V)alpha1 subfamily of voltage-gated K(+) channels in terminal arterioles from rabbit cerebral circulation. 2. K(+) current was measured from smooth muscle cells within intact freshly isolated arteriolar fragments. Current activated on depolarisation positive of about -45 mV and a large fraction of this current was blocked by 3,4-diaminopyridine (3,4-DAP) or 4-aminopyridine (4-AP), inhibitors of K(V) channels. Expression of cRNA encoding K(V)1.6 in Xenopus oocytes also generated a 4-AP-sensitive K(+) current with a threshold for activation near -45 mV. 3. Immunofluorescence labelling revealed K(V)1.2 to be specifically localised to endothelial cells, and K(V)1.5 and K(V)1.6 to plasma membranes of smooth muscle cells. 4. K(V) channel current in arteriolar fragments was blocked by correolide (which is specific for the K(V)alpha1 family of K(V) channels) but was resistant to recombinant agitoxin-2 (rAgTX2; which inhibits K(V)1.6 but not K(V)1.5). Heterologously expressed K(V)2.1 was resistant to correolide, and K(V)1.6 was blocked by rAgTX2. 5. Arterioles that were mildly preconstricted and depolarised by 0.1-0.3 nM endothelin-1 constricted further in response to 3,4-DAP, 4-AP or correolide, but not to rAgTX2. 6. We suggest that K(V)alpha1 channels are expressed in smooth muscle cells of terminal arterioles, underlie a major part of the voltage-dependent K(+) current, and have a physiological function to oppose vasoconstriction. K(V)alpha1 complexes without K(V)1.5 appear to be uncommon.

4-Aminopyridine↗
PubMed2001

Identification and pharmacological correction of a membrane trafficking defect associated with a mutation in the sulfonylurea receptor causing familial hyperinsulinism.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a genetic disorder characterized by excess secretion of insulin and hypoglycemia. In most patients, the disease is caused by mutations in sulfonylurea receptor-1 (SUR1), which, in association with Kir6.2, constitutes the functional ATP-sensitive potassium (K(ATP)) channel of the pancreatic beta-cell. Previous studies reported that coexpression of the PHHI mutant R1394H-SUR1 with Kir6.2 in COS cells produces no functional channels. To investigate if the loss of function could be due to impaired trafficking of mutant channels to the cell membrane, we have cotransfected wild-type and mutant SUR1 subunits with Kir6.2 into HEK293 cells and examined their cellular localization by immunofluorescent staining. Our results show that unlike the wild-type subunits, which showed fluorescence at the cell surface, the mutant subunits displayed fluorescence in punctate structures. Co-immunostaining with antibodies against organelle-specific marker proteins identified these structures as the trans-Golgi network. Limited localization in clathrin-positive, but transferrin receptor-negative vesicles was also observed. The post-endoplasmic reticulum localization suggests that the mutation does not impair the folding and assembly of the channels so as to cause its retention by the endoplasmic reticulum. Diazoxide, a K(ATP) channel opener drug that is used in the treatment of PHHI, restored the surface expression in a manner that could be prevented by the channel blocker glibenclamide. When expressed in Xenopus oocytes, R1394H-SUR1 formed functional channels with Kir6.2, indicating that the primary consequence of the mutation is impairment of trafficking rather than function. Thus, our data uncover a novel mechanism underlying the therapeutic action of diazoxide in the treatment of PHHI, i.e. its ability to recruit channels to the membrane. Furthermore, this is the first report to describe a trafficking disorder effecting retention of mutant proteins in the trans-Golgi network.

ATP-Binding Cassette Transporters↗
PubMed2001

TrpC1 is a membrane-spanning subunit of store-operated Ca(2+) channels in native vascular smooth muscle cells.

Mammalian counterparts of the Drosophila trp gene have been suggested to encode store-operated Ca(2+) channels. These specialized channels are widely distributed and may have a general function to reload Ca(2+) into sarcoplasmic reticulum as well as specific functions, including the control of cell proliferation and muscle contraction. Heterologous expression of mammalian trp genes enhances or generates Ca(2+) channel activity, but the crucial question of whether any of the genes encode native subunits of store-operated channels remains unanswered. We have investigated if TrpC1 protein (encoded by trp1 gene) is a store-operated channel in freshly isolated smooth muscle cells of resistance arterioles, arteries, and veins from human, mouse, or rabbit. Messenger RNA encoding TrpC1 was broadly expressed. TrpC1-specific antibody targeted to peptide predicted to contribute to the outer vestibule of TrpC1 channels revealed that TrpC1 is localized to the plasma membrane and has an extracellular domain. Peptide-specific binding of the antibody had a functional effect, selectively blocking store-operated Ca(2+) channel activity. The antibody is a powerful new tool for the study of mammalian trp1 gene product. The study shows that TrpC1 is a novel physiological Ca(2+) channel subunit in arterial smooth muscle cells.

Amino Acid Sequence↗
PubMed2001

Melanoma in African-Americans: trends in biological behavior and clinical characteristics over two decades.

BACKGROUND: The incidence of melanoma in the United States is increasing. Data on this disease in African-Americans is sparse. METHODS: Chart review of patients diagnozed with melanoma from 1975 to 1997 at Charity Hospital New Orleans (CHNO). Age, gender, anatomic distribution, histology, presenting stage, survival, and race were evaluated. RESULTS: Forty-four of 198 patients were African-American, of whom the majority developed cutaneous melanoma on the acral surface of the foot. African-American males were four times more likely to present with a cutaneous lesion than were African-American females. The median survival time for African-American with cutaneous lesions was 45 months, compared to 135 months for caucasians who were 3.6 times more likely to present with early disease (P < 0.05). TNM stage at presentation, and ulceration were significant, independent factors associated with a worse outcome in African-Americans. CONCLUSION: Overall survival time for African-Americans with cutaneous melanoma is significantly shorter than for caucasians with this disease. This trend may be attributable to the fact that African-Americans present with advanced disease. An increased level of awareness among both patients and health-care providers is necessary to identify African-Americans with melanoma at earlier stages of disease and to improve survival.

Adolescent↗
PubMed2001

Lung development: number of terminal bronchiolar duct endings and gas exchange surface area in victims of sudden infant death syndrome.

Previous research has demonstrated impaired renal development, particularly with respect to glomerular number, in victims of sudden infant death syndrome (SIDS). The present study used stereological principles to estimate the volume of the upper lobe of the right lung, total number of terminal bronchiolar duct endings (TBDE), and gas exchange surface area of this lobe within a group of human infants. The infants were classified according to cause of death (SIDS or non-SIDS), and further subdivided according to birth-weight: normal birth-weight (NBW) or low birth-weight (LBW). The results demonstrated that TBDE density was significantly reduced in SIDS compared to non-SIDS (P = 0.014), but only reduced from non-SIDS NBW values in the SIDS NBW group (P = 0.044). Total TBDE number was significantly reduced in SIDS from non-SIDS (P = 0.001), and was significantly reduced from non-SIDS NBW values in SIDS NBW (P = 0.023). Mean gas exchange surface area per TBDE was significantly increased in SIDS compared to non-SIDS cases (P = 0.049). The results of the present study indicate developmental delay of the lung in SIDS NBW infants who had previously not been considered growth retarded based on their normal body parameters.

Bronchi↗
PubMed2001

Rho-kinase inhibitors prevent agonist-induced vasospasm in human internal mammary artery.

1. Vasospasm of arterial conduits used for coronary artery surgery is an important cause of graft failure and is likely to result partly from raised levels of vasoconstrictor substances such as thromboxane A(2) and endothelin-1. Our aim was to find pharmacological agents that could prevent agonist-induced vasospasm. 2. Isometric tension was recorded from discarded segments of human left internal mammary artery (LIMA). Submaximal contraction evoked by the thromboxane A(2) mimetic U46619 (10 nM) was not inhibited by a blocker of store- and receptor-operated Ca(2+) channels (30 microM SKF96365) in the presence of diltiazem. Furthermore, contractions to < or =1 nM U46619 were preserved when extracellular Ca(2+) was reduced from 2.5 mM to 60 nM. Thus, sustained U46619-evoked contraction occurred without Ca(2+) influx. 3., We hypothesized that contraction might occur via Rho-kinase-mediated Ca(2+)-sensitization of myofilaments. Inhibitors of Rho-kinase (Y27632 and HA1077) were profound relaxants. If contraction was pre-evoked by 10 nM U46619, Y27632 and HA1077 caused full relaxation with EC(50)s of 1.67+/-0.22 microM and 3.58+/-0.35 microM respectively. Y27632 was also effective if applied before U46619, but was less potent. 4. Y27632 abolished contraction evoked by endothelin-1 and significantly reduced resting tone in the absence of a vasoconstrictor. 5. Rho-kinase-mediated Ca(2+)-sensitization appears to be a major mechanism of vasoconstriction in human LIMA. Rho-kinase inhibitors may have an important role in preventing vasospasm in arterial grafts used for coronary artery surgery.

Calcium↗
PubMed2001

Stereological estimation of eye volume using the Pappus method.

The estimation of object volume from rotationally randomised sections relies on an ancient geometrical principle due to the Alexandrian mathematician Pappus. In this paper we describe two studies that make estimates of eye volume using a stereological version of the Pappus principle. The first study uses a design-based version of the Pappus theorem to make estimates of eye volume in Sprague-Dawley rats and the second uses a model-based implementation for estimating eye volume in juvenile Dover sole. In the sole study we compare the estimates of volume with estimates made using the Cavalieri method and show that the Pappus method gives identical volume estimates with a markedly lower coefficient of variation (2.5%) than the Cavalieri method (13.5%).

Animals↗
PubMed2001

Drugs, guns, and kids: the association between substance use and injury caused by interpersonal violence.

BACKGROUND: Drug and alcohol uses have been linked to the frequency of injury events, recurrent hospital admission for injury, and interpersonal violence. Data regarding the association of recent substance use and injury type and frequency in children and young adults are not available. Such data probably would be valuable in planning interventions to prevent substance use and reduce the risks of injuries. METHODS: Evidence of substance use was assessed in trauma patients presenting to the authors' level 1 trauma center over a 6-month interval. Demographic data, mechanisms of injury, revised trauma scores (RTS), injury severity scores (ISS), hospital days, and mortality rate were evaluated. Chi square analysis and 2-tailed, paired t tests were used for statistical analysis. Multivariate logistic regression was utilized to determine the influence of individual variables. RESULTS: From a total group of 743 patients with life-threatening injuries, trauma registry records of 186 patients less than 21 years old were eligible for evaluation, and 126 of these had complete blood and urine drug assessments completed on admission to the trauma center. Forty-two percent (53 of 126) patients tested positive for alcohol or drugs. No patients less than 14 years of age (n = 61) had positive drug screen results. However, in the cohort of patients aged 14 and 15 (n = 17), 71% tested positive. Also, 72% of adolescents (age < 18) who were victims of injuries from gunshot wounds had evidence of substance use. Multivariate analysis showed gunshot wounds (P <.003) to be associated independently with positive drug screens. No statistical differences were observed in ethnic distribution, ISS, RTS, hospital days, or mortality rate when patients with positive screen results were compared with those without evidence of substance use. CONCLUSIONS: Trauma victims had evidence of substance use in early teen age years especially in the 14 and 15-year-old age groups. Toxicology screening disclosed that substance use is associated strongly with gunshot wounds. Substance use, along with poverty, inadequate family support, and peer pressure are factors that influence injury risk. Interventions to prevent substance use in young children may reduce the risk of injury.

Adolescent↗
PubMed2001

Age bias: a cause of underutilization of breast conservation treatment.

BACKGROUND: Breast conservation therapy (BCT) has been shown to result i about the same disease control and survival as modified radical mastectomy (MRM) for stage I and II breast cancers. Barriers to using BCT in patients with invasive breast cancer include "physician preference." This study was undertaken to investigate the bias of residents with respect to breast-conserving procedures. METHODS: Internal medicine and surgery residents were instructed about the efficacy of BCT. Subsequently, their opinions were assessed using a questionnaire concerning recommendations for BCT versus MRM as well as breast reconstruction after MRM in similar patients. Chi square tests were used for statistical analysis. RESULTS: Seventy-nine residents (54 medical, 25 surgical) participated. MRM was recommended for 38% of older (> 59 years old) versus 11% of younger patients (< 31 years old), p < 0.01. Furthermore, breast reconstruction was recommended for 96% of younger versus only 70% of older patients (p < 0.01). CONCLUSIONS: Residents are biased against older women in their recommendations for breast conservation and breast reconstruction. Educational efforts to decrease this age bias should be instituted during residency.

Adult↗
PubMed2001

Ageism in medical students' treatment recommendations: the example of breast-conserving procedures.

PURPOSE: Age bias may play a role in physicians' discussions of equivalent therapeutic options with patients, especially in respect to breast-conservation therapy. This study investigated bias based on age (ageism) among physicians-in-training in their treatment recommendations for breast-conserving procedures. METHOD: Second-year medical students responded to a questionnaire concerning recommendations they would make for breast conservation or mastectomies with or without breast reconstruction for eight patients with similar-stage breast cancer. The patients differed by age (older were > or =59 years, younger < or =31 years), race, and marital status. A total of 116 students made 1,146 recommendations. Percentages of the students' recommendations for breast-conservation therapy (BCT) were calculated for the two patient age groups and for the recommendations for breast reconstruction after the patient had already chosen modified radical mastectomy (MRM). Chi-square tests were used for statistical analysis. RESULTS: The students recommended BCT for a significantly higher percentage of younger patients than older patients (86% versus 66%; p<.001). They recommended MRM to 34% of older patients versus 14% of younger patients (p<.001). Furthermore, the students recommended breast reconstruction after MRM to a significantly higher percentage of younger patients than older patients (95% versus 65%; p<.001). CONCLUSIONS: Medical students' recommendations of breast conservation and breast reconstruction showed age bias. Educational efforts should be instituted during the medical school to decrease ageism in students' treatment recommendations.

Adult↗
PubMed2001

K(V)alpha1 channels in murine arterioles: differential cellular expression and regulation of diameter.

The primary objectives of this study were to reveal cell-specific expression patterns and functions of voltage-gated K(+) channel (K(V)alpha1) subunits in precapillary arterioles of the murine cerebral circulation. K(V)alpha1 were detected using peptide-specific antibodies in immunofluorescence and Western blotting assays. K(V)1.2 was localized almost exclusively to endothelial cells, whereas K(V)1.5 was discretely localized to the nerves and nerve terminals that innervate the arterioles. K(V)1.5 also localized specifically to arteriolar nerves in human pial membrane. K(V)1.5 was notable for its absence from smooth muscle cells. K(V)1.3, K(V)1.4, and K(V)1.6 were localized to endothelial and smooth muscle cells, although K(V)1.4 had a low expression level. K(V)1.1 was not expressed. Therefore, we show that different cell types of pial arterioles have distinct physiological expression profiles of K(V)alpha1, conferring the possibility of differential modulation by extracellular and second messengers. Furthermore, we show recombinant agitoxin-2 and margatoxin are potent vasoconstrictors, suggesting that K(V)alpha1 subunits have a major function in determining arteriolar resistance to blood flow.

Animals↗
PubMed2001

Organogenesis of lung and kidney in Thoroughbreds and ponies.

Equine lung and kidney organogenesis has not previously been examined with the use of unbiased stereological techniques. The present study examined healthy (control) pony and Thoroughbred lungs and kidneys to establish baseline data of organ development from before birth until maturity at age 3-18 years. Whole left lungs and kidneys were collected from 45 equine postmortem examinations (34 Thoroughbred, 11 pony). Stereological techniques were used to estimate whole kidney, cortex and medulla volume, total glomerular number and volume-weighted mean glomerular volume, lung volume, total terminal bronchiolar duct ending number and total gas exchange surface area. Lungs were demonstrated to be more developed at birth in ponies compared with Thoroughbreds. Thoroughbreds showed continued lung development after birth, a unique micromorphogenic postnatal development. Kidneys were developed equally in ponies and Thoroughbreds. This study has provided data on the baseline development of the equiune lung and kidney which can be used in further studies to examine whether the development of these organs is affected by specific illnesses.

Animals↗
PubMed2001

Axillary lymph node status of T1 primary breast cancer in a diverse population.

The utility of level I and II axillary lymph node dissection in women with primary tumors less than 1 cm in diameter has recently received extensive evaluation. Numerous patients undergo axillary lymph node dissection ultimately to discover no pathological involvement. This study investigates the lymph node status in T1 primary breast adenocarcinoma in our diverse patient population. A retrospective evaluation of patients treated at the Medical Center of Louisiana at New Orleans and the Tulane University Medical Center with breast adenocarcinoma less than or equal to 2 cm was performed. Demographic data and pathological reports were reviewed to obtain breast lesion size and lymph node status. One hundred sixteen patients were found to have T1 lesions. Ethnic distribution was African American 66 per cent; Caucasians 30 per cent; Hispanic 2 per cent; and Asian 3 per cent. Whereas no patients with T1a lesions had positive lymph nodes, 11 per cent of patients with T1b lesions and 36 per cent of patients with T1c lesions had positive lymph nodes. However, in our patient population no patients with tumors less than 1.0 cm. in diameter had positive lymph nodes. Although this may be due to our relatively small sample size axillary lymph node dissection may be unnecessary in this select patient population. For patients with lesions 1.0 cm and greater an axillary lymph node dissection seems to add necessary information for correct treatment in a small percentage of patients. The use of lymphatic mapping with sentinel axillary lymph node biopsy may reduce the number of unnecessary axillary dissections in early breast cancer.

Adenocarcinoma↗
PubMed2001

Magnification views of mammography decrease biopsy rates.

Mammography is a valuable tool for screening and has increased early detection of breast cancer. Magnification views are commonly used to further elucidate suspicious changes seen on routine mammograms. The effect of magnification views and their utility have not been studied regarding the influence on treatment strategies. All patients who had magnification views performed along with their mammogram at Tulane University Medical Center over a one-year period were included. Patient charts were reviewed for mammogram readings, recommendations, and any biopsy results. The original mammograms without the magnification views were given to a physician who was blinded to the final results of the magnification views for a recommendation of whether or not to biopsy the lesion. These recommendations were compared with the results with actual recommendations. Magnification views were performed on 127 patients. After the additional magnification views were taken 27 per cent (34 of 127) of patients had biopsies performed. Biopsy results revealed benign findings in 71 per cent and nonbenign findings (lobular carcinoma in situ, ductal carcinoma in situ, or carcinoma) in 29 per cent. On the basis of the recommendations without magnification views 64 per cent of patients would have had biopsies performed. Magnification views decreased the biopsy rates by 58 per cent (P < 0.001; chi2 tests). Magnification views can help decrease the number of biopsies performed for suspicious small areas on mammograms. Their judicious use can help decrease unnecessary procedures, patient anxiety, and cost. Magnification views are useful to help surgeons and radiologists best screen for breast cancer.

Biopsy↗
PubMed2000

PH20: a novel tumor marker for laryngeal cancer.

OBJECTIVE: To determine whether levels of PH-20, a hyaluronidase similar to that found in human sperm, are elevated in laryngeal cancer tissue. DESIGN: In this case-control study. reverse transcription polymerase chain reaction was used to measure levels of PH-20 messenger RNA in tissue taken from laryngectomy specimens. SETTING: A university medical center. PATIENTS: We compared tissue samples taken from 11 patients with laryngeal cancer, and from 2 metastatic lymph nodes, with samples of normal, healthy laryngeal tissue and prostate cancer tissue (positive control). MAIN OUTCOME MEASURE: PH-20 complementary DNA expression as quantified by densitometric analysis. RESULTS: Expression of PH-20 was significantly higher in nonirradiated laryngeal cancer specimens than in normal laryngeal tissue (P<.01). Metastatic lymph nodes also had higher levels of PH-20 expression than did primary laryngeal cancer tissue (P = .11) and normal laryngeal tissue (P<.01). Irradiated laryngeal cancer specimens had PH-20 levels comparable to normal. CONCLUSIONS: We report the first data on PH-20 expression in laryngeal cancer tissue. PH-20 expression is significantly elevated in primary laryngeal cancer tissue and seems to be even higher in metastatic lesions compared with normal laryngeal tissue. PH-20 may be a useful tumor marker and prognostic tool for laryngeal cancer.

Biomarkers, Tumor↗