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Biomedical subjects

S E Greer

Publications and source records attributed to S E Greer.

At least 19 recordsLinked to original sources
PubMed2001

Subatmospheric pressure dressing for saphenous vein donor-site complications.

Newer endoscopic techniques have been successful at reducing saphenous vein donor-site wound complications, but not entirely eliminating them. Tissue necrosis with superimposed infection is typically treated with antibiotics and surgical debridement. Typically, primary reclosure is not possible and the open leg wound is allowed to slowly granulate with dressing changes until a skin graft can be performed. This report describes an alternative treatment using subatmospheric pressure dressing to promote granulation tissue and wound closure in saphenous vein donor-site wounds.

Aged↗
PubMed2001

Comprehensive analysis of citrate effects during plateletpheresis in normal donors.

BACKGROUND: Although plateletpheresis procedures are generally well tolerated, the clinical and metabolic consequences associated with rapid infusion of up to 10 g of citrate are underappreciated, and a comprehensive description of these events is not available. STUDY DESIGN AND METHODS: Clinical and laboratory changes were studied in seven healthy donors undergoing three 90-minute plateletpheresis procedures each, at continuous, fixed citrate infusion rates of 1.1, 1.4, and 1.6 mg per kg per minute. RESULTS: Serum citrate levels increased markedly with increasing citrate infusion rates and did not achieve a stable plateau. As citrate infusion rates increased, the total volume processed and platelet yields also increased, but donor symptoms became more severe. Ionized calcium (iCa) and ionized magnesium (iMg) concentrations decreased markedly, by 33 and 39 percent below baseline, respectively, at a citrate rate of 1.6 mg per kg per minute. Intact parathyroid hormone levels were higher at 30 minutes than at later time points, despite progressive decreases in iCa and iMg. Urine citrate, calcium, magnesium, sodium, and potassium concentrations and urine pH values increased markedly during all procedures. CONCLUSION: Marked, progressive increases in serum citrate levels occur during plateletpheresis, accompanied by symptomatic decreases in iCa and iMg, with significantly increased renal excretion of calcium, magnesium, and citrate.

Adult↗
PubMed2001

Importance of the nasal-to-cervical relationship to the profile in rhinoplasty surgery.

There is general agreement that when discussing surgery with the prospective rhinoplasty patient, one may also include discussion of the chin because of the important interrelationship between these two regions. It is apparent that on the profile-lateral view, the four prominences-the forehead, nose, chin, and neck-balance and complement one another. The cervical region, the fourth dimension, was examined to estimate the aesthetic significance of the nasal-to-cervical relationship and to determine the implications to rhinoplasty surgery. Part I of the study was a survey to test the hypothesis that the cervical region affects the perceived impression of the nose. Four standard facial-profile black-and-white photographs were chosen to represent varying degrees of nasal dorsum hump and cervical ptosis problems. Using computer-altering software, only the cervical regions were altered to create a pair of photographs for each of the four profiles: one with a youthful-looking non-ptotic cervical region, the other with a ptotic aged-looking cervical region. Raters were asked to give their first-impression opinions of which nose subjectively appeared "better." Raters consistently (84 percent of the time) chose the nose on the faces with the less ptotic neck as being better. Therefore, a less ptotic neck improved the perceived appearance of the nose. Part II was a retrospective chart review of the rhinoplasty patients of a single surgeon by independent raters. To estimate the aesthetic significance of the nasal-to-cervical relationship, the proportion of patients undergoing rhinoplasty surgery who could have potentially benefited from a youth-restoring neck procedure was determined. Criteria originally described by Ellenbogen and Karlin for judging the results of youth-restoring neck procedures were used as relative indications for neck surgery. An average of 27.2 percent of the patients did not have visible criteria and therefore by definition had relative indications for neck-rejuvenating procedures when undergoing rhinoplasty surgery. As demonstrated in part I of the study, improving the neck could improve the perceived results of the rhinoplasty. Part III of the study validated the Ellenbogen and Karlin criteria. The present authors found that the original criteria were probably based on female patients, that male and older patients had more indications for surgery, and that there was significant interrater agreement with the youthful criteria. In summary, the authors established that a strong nasal-to-cervical relationship exists whereby the perceived appearance of the nose is affected by the neck. The significance of this relationship to rhinoplasty surgery was determined, and it was found that more than 27 percent of rhinoplasty patients could obtain better perceived nasal results with a concomitant neck-rejuvenating procedure. Consequently, discussing neck-rejuvenating procedures with the rhinoplasty patient is valuable.

Adolescent↗
PubMed2000

The use of subatmospheric pressure dressing therapy to close lymphocutaneous fistulas of the groin.

Groin lymphorrhea is an uncommon but serious complication of vascular and cardiac surgery as well as interventional procedures that cannulate the femoral vessels. Treatment options are somewhat controversial. For lymphocutaneous fistulas, a commonly used current modality is early surgical ligation with the assistance of blue-dye staining of the lymphatic anatomy. The purpose of this case series is to give the first description of a new, less invasive, approach using subatmospheric pressure dressing therapy for the treatment of the challenging problem of lymphocutaneous fistulas of the groin.

Aged↗
PubMed2000

The true hanging columella: simplified diagnosis and treatment using a modified direct approach.

An imbalance between the alar rim and the columella border can be a disturbing aesthetic deformity. If the cause is a pseudohanging columella, the therapy should be directed to the alar rims. When the deformity is a true hanging columella with unusually wide medial crural cartilages, balance can be restored by excising a C-shaped crescent of cartilage from the cranial border of the medial crura of the alar cartilages in a direct approach. This condition was present in approximately 15 percent of the patients reviewed. The treatment of a true hanging columella adds a subtle beneficial enhancement to the results of a rhinoplasty. The authors describe a simplified diagnostic method and present their experience treating the true hanging columella using a modified "direct approach" through a closed endonasal rhinoplasty.

Adult↗
PubMed2000

Energy taxis is the dominant behavior in Azospirillum brasilense.

Energy taxis encompasses aerotaxis, phototaxis, redox taxis, taxis to alternative electron acceptors, and chemotaxis to oxidizable substrates. The signal for this type of behavior is originated within the electron transport system. Energy taxis was demonstrated, as a part of an overall behavior, in several microbial species, but it did not appear as the dominant determinant in any of them. In this study, we show that most behavioral responses proceed through this mechanism in the alpha-proteobacterium Azospirillum brasilense. First, chemotaxis to most chemoeffectors typical of the azospirilla habitat was found to be metabolism dependent and required a functional electron transport system. Second, other energy-related responses, such as aerotaxis, redox taxis, and taxis to alternative electron acceptors, were found in A. brasilense. Finally, a mutant lacking a cytochrome c oxidase of the cbb(3) type was affected in chemotaxis, redox taxis, and aerotaxis. Altogether, the results indicate that behavioral responses to most stimuli in A. brasilense are triggered by changes in the electron transport system.

Air↗
PubMed1999

Boxer's fracture: an indicator of intentional and recurrent injury.

The objective was to describe the population of patients presenting with a boxer's fracture (BF), to determine how often BF is an intentional injury, to determine if it is a predictor of recurrent injury, and to compare the rates of intentional injury and injury recidivism between patients with BF and those with other injuries. An emergency department (ED)-based injury surveillance system (EDBISS) in a university-affiliated ED (census of 35,000) provided data on injured patients presenting between January 1, 1995 and December 31, 1996. Chart review was performed. Descriptive analyses were performed. The results showed 22,728 of 69,438 (33%) ED visits during a 2-year period were attributable to injuries. Sixty-two patients presented with BF. Mean age of BF patients was 22.1 versus 28.6 for all injured (P < .005). Ninety-two percent (57/62) of BF patients were men compared with 58% of all injured (P < .0001). Thirty-eight of 62 (61%) BF injuries were sustained after intentional punches of an object/person. Seventeen of 62 (27%) BF patients were injury recidivists. Previous studies in this same ED population showed that 6% had intentional injuries and 12% were injury recidivists. BF is usually an intentional injury and these patients are at increased risk for recurrent injury. Clinicians should focus prevention efforts on this high-risk population.

Adolescent↗
PubMed1999

Techniques for applying subatmospheric pressure dressing to wounds in difficult regions of anatomy.

Subatmospheric pressure dressing (SPD) has been commercially available in the United States since 1995 as the vacuum-assisted closure (VAC) device. SPD increases local blood flow, decreases edema and bacterial count, and promotes the formation of granulation tissue. Despite recent clinical successes with the use of SPD in a variety of wound types, problems may occur with application of VAC system in certain areas of the body. The main limitation occurs when attempting to maintain an airtight seal over irregular surfaces surrounding a wound. For example, application of the adhesive drape and creation of a seal are particularly difficulty in the hip and perineum. In addition, wounds of the lower extremity can occur in multiple sites, posing the problem of providing a vacuum dressing to more than one wound from one suction pump machine. To address these challenging clinical wounds, we have developed techniques to allow the successful application of SPD to sacral pressure ulcers near the anus, and to multiple large lower extremity ulcers.

Adhesives↗
PubMed1999

The use of subatmospheric pressure dressing for the coverage of radial forearm free flap donor-site exposed tendon complications.

Since its description in China in 1978, the radial forearm free flap has become a workhorse for the reconstructive surgeon. However, the flap has known disadvantages in complications of the wrist donor site. Skin graft breakdown with exposure of the flexor tendons of the wrist is the most common. The authors describe in a patient series a new treatment for this complication. They used subatmospheric pressure dressing to stimulate granulation tissue coverage of the tendon and to facilitate epithelialization. As many as one third of all patients undergoing radial forearm free flaps develop exposed tendon complications and may benefit from Vacuum Assisted Closure (VAC) therapy.

Aged↗
PubMed1994

Evidence that Ca(2+)-activated K+ channels participate in the regulation of pituitary prolactin secretion.

We evaluated the role of Ca(2+)-activated K+ channels in the regulation of prolactin (PRL) secretion with a perifusion system using acutely dispersed rat anterior pituitary cells. Apamin, which blocks Ca(2+)-activated K+ channels, induced PRL secretion in a dose-dependent fashion between 1 and 300 nM (r = 0.99, P < 0.01). Charybdotoxin, another Ca(2+)-activated K+ channel-blocker, also induced PRL secretion at 20 nM concentration. These were not non-specific toxic effects, since stimulation of PRL secretion by 10 nM thyrotropin-releasing hormone (TRH) was not different before and after applying the channel-blockers. Both 10 microM dopamine and 2 microM nifedipine significantly, but incompletely, depressed PRL secretion induced by 100 nM apamin; 10 microM dopamine completely blocked PRL secretion induced by 20 nM charybdotoxin. Our data indicate that Ca(2+)-activated K+ channels may play an important role in the regulation of PRL secretion.

Animals↗
PubMed1994

Evidence that tolbutamide induces prolactin secretion by a mechanism which does not involve blocking ATP-sensitive potassium channels.

Tolbutamide is an important member of the sulfonylureas, drugs which stimulate secretion of several hormones, including insulin and prolactin (PRL), through a mechanism postulated to involve blocking ATP-sensitive K+ channels. In the present study, we have evaluated the hypothesis relating the induced secretion to an effect on K+ channels by examining the effect of tolbutamide and the ATP-sensitive K+ channel-opener, diazoxide, on PRL secretion by acutely dispersed perifused adenohypophyseal cells from young adult male rats. Five-min perifusion of 0.1-50 microM tolbutamide induced a concentration-correlated secretion of PRL with a minimum effective concentration of 0.1 microM. Both basal and 50 microM tolbutamide-induced PRL secretion were significantly suppressed by 10 microM dopamine or 2 microM nifedipine, which block Ca2+ influx through L-type channels, but not by 100 microM diazoxide, indicating that tolbutamide induces PRL secretion by a mechanism involving Ca2+ influx through L-type Ca2+ channels which is not related to its ability to block ATP-sensitive K+ channels.

Adenosine Triphosphate↗
PubMed1994

Rat Prl and TSH secretion are regulated differently by K(+)-channel blockers.

All four different K(+)-channel blockers [tetraethylammonium (TEA), a nonselective K(+)-channel blocker; tolbutamide, an ATP-sensitive K(+)-channel blocker; quinine and 4-aminopyridine, both primarily voltage-dependent K(+)-channel blockers] stimulated prolactin (Prl) secretion by acutely dispersed anterior pituitary cells but had no effect on thyroid-stimulating hormone (TSH) secretion. TEA stimulated Prl secretion in a dose-dependent manner between 1 microM and 20 mM, but even as high as 20 mM, TEA did not induce TSH secretion. Valinomycin (2 microM), a K+ ionophore, inhibited both basal and TEA-induced Prl secretion. TEA-stimulated Prl secretion was abolished by using a Ca(2+)-depleted medium or adding 10 microM dopamine. TEA did not reverse the inhibitory effect of dopamine on thyrotropin-releasing hormone-induced Prl secretion. Our data indicate that K+ channels may play a role in the secretion of adenohypophysial hormones that is idiosyncratic for each hormone. Differences in the role of K+ channels may reflect differences between the various pituitary cell types in plasma membrane ion channel composition, membrane potential, or the mechanism of exocytosis.

Animals↗
PubMed1993

Adenosine 3',5'-cyclic monophosphate-mediated prolactin secretion in GH4C1 cells involves Ca2+ influx through L-type Ca2+ channels.

In normal anterior pituitary cells adenosine 3',5'-cyclic monophosphate (cAMP)-mediated prolactin (PRL) secretion requires Ca2+ influx. However, the role of Ca2+ in cAMP-induced secretion in the clonal rat pituitary tumor-derived GH4C1 cells remains uncertain. We examined in GH4C1 cells the effects of forskolin (FSK), an adenylate cyclase activator, and dibutyryl cAMP (DB-cAMP) on PRL secretion and intracellular Ca2+ ([Ca2+]i) dynamics. Ca2+ depletion of the medium inhibited FSK and DB-cAMP stimulated PRL secretion approximately 50%. Both FSK and DB-cAMP increased [Ca2+]i in a dose-dependent fashion. The peak amplitude in [Ca2+]i in response to each concentration of these stimuli was achieved in 3 min, corresponding to the peak PRL response to the same stimuli. Either Ca2+ depletion of the medium or addition of 2 microM nifedipine (NF) abolished the increase in [Ca2+]i caused by FSK or DB-cAMP. Our data indicate that an increase in intracellular c-AMP in GH4C1 cells produces an elevation of [Ca2+]i by opening L-type Ca2+ channels and that c-AMP-mediated PRL secretion is augmented by Ca2+ influx in GH4C1 cells as in normal pituitary cells.

Adenylyl Cyclases↗
PubMed1993

Evidence that the major physiological role of TRH in the hypothalamic paraventricular nuclei may be to regulate the set-point for thyroid hormone negative feedback on the pituitary thyrotroph.

If a primary physiologic action of TRH is to regulate the set-point for negative feedback, a sudden drop in plasma thyroid hormone concentration should stimulate the same rate of in vivo increase in TSH secretion from normal and TRH-deprived thyrotrophs. To test this hypothesis, 3 experiments were performed in which young adult female rats were divided into 3 groups of 6-10 rats each: intact controls, hypothalamic paraventricular nuclei ablation (PVN) and sham-ablated (Sham). Sham and PVN rats were thyroparathyroidectomized 2-4 weeks after brain lesions and serial blood samples taken in all groups at frequent intervals from 0 to 58 days post-thyroidectomy. Plasma TSH was significantly higher than in intact controls by 3 days post-thyroidectomy in both the Sham and PVN groups (p < 0.05). At 14 days PVN plasma TSH was 4 x higher and at 30 days 8 x higher than in intact controls and remained consistently at 50% of that of the Sham group. There was no statistical difference between PVN and Sham in the rate of increase in TSH. Plasma T4 was 40% lower in PVN than in Sham at the time of thyroidectomy and became undetectable in both by day 3. The prompt parallel rate of rise of plasma TSH in Sham and PVN groups following thyroidectomy indicates that a primary physiologic action of TRH in the thyrotroph is to control the set-point for thyroid hormone negative feedback on TSH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Isotonic but not hypertonic ethanol stimulates LHRH secretion from perifused rat median eminence.

We utilized luteinizing hormone-releasing hormone (LHRH) secretion by perifused minced rat hypothalamic median eminence (ME) tissue to evaluate whether isotonic ethanol would stimulate neurosecretion as it does secretion from pituitary cells. Isotonic ethanol induced a dose-dependent burst of LHRH secretion which was maximal at 2-3 min and returned to near baseline by 10 min. In Ca(2+)-depleted media (< 2 microM Ca2+), stimulation of secretion by isotonic ethanol was enhanced, but secretion induced by depolarizing 30 mM K+ was abolished. Hypertonic ethanol was ineffective in stimulating LHRH secretion in either normal or Ca(2+)-free media. The secretory response of hypothalamic LHRH-secreting cells to ethanol and its negative modulation by medium Ca2+ is thus identical to that of normal anterior pituitary cells and presumably is caused by cell swelling resulting from influx of permeant ethanol molecules across the plasmalemma.

Animals↗
PubMed1992

Cell swelling induced by medium hyposmolarity or isosmolar urea stimulates gonadotropin-releasing hormone secretion from perifused rat median eminence.

Medium hyposmolarity between 10 and 50% and isotonic urea between 22.5 and 90 mM induced a dose-dependent burst of gonadotropin-releasing hormone (GnRH) secretion from perifused median eminence tissue which was maximal at 2-3 min and returned to near baseline by 5 min in spite of continued exposure to the stimulus. If Ca(2+)-free medium was used, osmotic stimulation of secretion was increased or unchanged, but secretion induced by 30 mM K+ was markedly reduced. Our data indicate that cell swelling induced by medium hyposmolarity or permeant molecules stimulates GnRH secretion from median eminence cells or cell processes as it does secretion from normal endocrine cells containing hormone stored in intracellular vesicles. In both, Ca2+ influx is not required or has a negative modulating influence on cell swelling-induced secretion.

Animals↗