Characterization of the mid-coronal plane method for measurement of radiographic change in knee joint space width across different levels of image parallax.

OBJECTIVE: Radiographic measurement of the change in knee joint space width (ΔJSW) is often affected by image parallax, which causes an apparent exaggeration of JSW due to projectional differences. This issue with parallax (quantified by intermargin distance) can in part be addressed with a novel mid-coronal plane (MCP) measurement method. The objectives of the study were to determine 1) accuracy and 2) reproducibility of the MCP method, and 3) compare the MCP method to that used in the Osteoarthritis Initiative (OAI) for different categories of parallax. METHODS: Posteroanterior radiographs (n = 70) with known JSW were digitally reconstructed from CT images of cadaver knees and used to determine the accuracy of ΔJSW using the MCP method for parallax categories of None, Mild/Moderate, and Severe. Reproducibility was determined from pairs of clinical radiographs selected from the OAI (n = 170). The MCP method was also compared to the OAI methodology. Both reproducibility and agreement were characterized by Bland-Altman analysis and intraclass correlation coefficients (ICC). RESULTS: The MCP method was accurate to 0.11 mm in cases with no parallax, and 0.18 mm across all categories of parallax for medial and lateral compartments. Reproducibility of the MCP method was graded "excellent" (ICC 0.98, 95% CI [0.98, 0.99]). The MCP results agreed very well with the OAI (ICC 0.92, 95% CI [0.89, 0.94]), with mean absolute differences between methods increasing with increasing parallax. CONCLUSION: The MCP method is an accurate, reproducible alternative to the OAI method for multi-center clinical trials where subject and X-ray beam positioning may be variable.

A comparison between videotaped and live demonstrations, for the teaching of removable partial denture procedures.

AIM: This study was devised to test the effectiveness of videotaped demonstrations as opposed to live demonstrations, to small groups of undergraduate dental students. The outcome was assessed by comparing the students' understanding of the clinical and laboratory technical stages of the altered cast impression technique, which is used in the construction of removable partial dentures. METHOD: 31 students watched a series of videotaped demonstrations and 30 received a similar series of live demonstrations. The altered cast procedure was divided into 5 distinct stages, each of which was assessed with the aid of agreed criteria, initially by the students and then by 2 staff assessors and these results were compared. The students were subsequently asked to rate how helpful the videotaped or live demonstration had been on a 5-point scale. RESULTS: The live demonstration group showed better agreement between the students' assessment and the assessors' assessment of the quality of the work for the first part of the clinical stage. There was no difference in the groups' assessment of the final outcome of this clinical stage and the subsequent laboratory technical stages. Students who observed the live demonstrations indicated higher scores for its helpfulness in performance of all the stages of the technique, when compared to those who had observed a videotaped demonstration. CONCLUSION: Both teaching methods developed a similar level of understanding of the principles behind the exercise, although the students preferred the live demonstrations. A carefully produced videotaped demonstration can be a useful alternative to a live demonstration in teaching the short and clear cut technique selected for this study.

Multiple polyamine regulatory pathways control compensatory cardiovascular hypertrophy in coarctation hypertension.

While a number of factors may initiate structural alterations within the cardiovascular system in response to hypertension, there are obligate cellular signaling mechanisms, such as the polyamines, through which they must operate. This study examined the effects of polyamine synthesis inhibition using eflornithine, a suicide inhibitor of ornithine decarboxylase on blood pressure, compensatory remodeling of the cardiovascular system, and cardiac and aortic polyamine contents using an aortic coarctation model in rats. Eflornithine treatment failed to reduce carotid arterial blood pressure and actually significantly elevated vascular pressure above and below the coarctation site by 14 days of hypertension. Eflornithine only transiently reduced aortic polyamine content of hypertensive rats while this agent reduced coarctation-induced aortic medial wall thickening and the synthesis/deposition of fibronectin and laminin in the hypertensive aorta. Increases in left ventricular mass and polyamine content were concomitantly reduced in hypertensive rats administered eflornithine. These results suggest that multiple polyamine regulatory pathways may maintain vascular polyamine content in response to aortic coarctation; however de novo polyamine synthesis is essential for select aspects of vascular remodeling, including matrix synthesis. Cardiac tissue, in contrast, may rely principally on de novo polyamine synthesis.

Eflornithine alters changes in vascular responsiveness associated with coarctation hypertension.

This study examined the temporal effects of the polyamine synthesis inhibitor eflornithine (alpha-difluoromethylornithine) on vascular responses to KCI, norepinephrine, sodium nitroprusside and acetylcholine in aortic rings from coarctation hypertensive rats. Coarctation hypertension reduced the contractile response of aortic rings to KCI and norepinephrine, increased sensitivity (reduced the EC50 value) to norepinephrine and attenuated relaxation to acetylcholine by 14 days of hypertension. Treatment of coarctation hypertensive rats with eflornithine resulted in a normalization of the contractile intensity to KCI and norepinephrine and relaxations to acetylcholine by 14 days of hypertension. Responses to sodium nitroprusside were similar in all groups at all time points. Hyperresponsiveness to norepinephrine produced by coarctation of the aorta was not affected by eflornithine. These studies indicate that normalization of vascular function can occur in the presence of significantly elevated blood pressure upon chronic administration of eflornithine. This functional normalization correlates with eflornithine-mediated regression of structural abnormalities normally associated with pressure overload hypertension.

Technetium Tc 99m rapidly crosses the ovine placenta and intramembranous pathway.

OBJECTIVE: This study examined the movement of the soluble ion technetium Tc 99m across the ovine placenta and intramembranous pathway. STUDY DESIGN: Nineteen fetal sheep at 131 +/- 1 (SE) days' gestation were studied. After a 1-hour control period technetium Tc 99m was injected into either a fetal vein (n = 7), the amniotic cavity (n = 5), or a maternal vein (n = 5). Maternal and fetal blood, fetal urine, and amniotic and allantoic fluid were sampled during the control period and for 8 hours after the injection. Fetal urine was drained externally throughout the experiment. In five animals technetium Tc 99m was injected intraamniotically after the fetus was killed with air emboli and sampled as described. RESULTS: Intrafetally injected technetium Tc 99m rapidly crossed the placenta; then it entered and was concentrated in the amniotic cavity. Intraamniotically injected technetium Tc 99m rapidly entered into the fetal circulation. The maternally injected technetium Tc 99m rapidly crossed the placenta into the fetus, suggesting a half-time for placental exchange of < 50 minutes. The technetium Tc 99m injected into the dead fetus group demonstrated significantly less maternal absorption than in the live fetus group. CONCLUSIONS: The soluble ion technetium Tc 99m demonstrated a much more rapid movement in both directions across the ovine placenta then previously demonstrated for the smaller ion sodium. Technetium Tc 99m rapidly crossed the intramembranous pathway bidirectionally, suggesting a high permeability of the intramembranous pathway. Minimal maternal absorption of technetium Tc 99m in the dead fetus group suggests little transmembranous absorption by the mother.

RGD-containing peptides induce endothelium-dependent and independent vasorelaxations of rat aortic rings.

Peptides containing the extracellular matrix peptide cell attachment sequence RGD possess potent, endothelium-dependent vasorelaxant properties. In the present study, the ability of RGD-containing peptides to cause vasorelaxation in the presence and absence of a functional endothelium was examined in rat aortic rings along with the ability of RGD-containing peptides to increase cGMP production in these vessels. The active RGD-containing peptide GRGDNP induced rapid relaxation in endothelium-intact, norepinephrine contracted rat aortic rings. When the endothelium was removed, RGD-containing peptides produced a slow relaxation of contracted rings which took approx. 40 min to reach maximum relaxation. Control RGD peptides were without effect either in the presence or absence of a functional endothelium. While acetylcholine and sodium nitroprusside stimulated cGMP production in endothelium-intact and denuded aortic segments, neither the control RGD peptide nor the active GRGDNP increased cGMP in these vessels when compared to controls upon either short (30 s) or long (45 min) incubation times. These data indicate that relaxations of rat aortic rings in response to RGD-containing peptides occur both in the presence and absence of an intact endothelium and that cGMP is likely not the sole mediator of these responses.

Potential route for fetal therapy: intramembranous absorption of intraamniotically injected furosemide.

OBJECTIVE: Our purpose was to determine whether intraamniotically injected furosemide could be absorbed directly into fetal circulation by the ovine intramembranous pathway. STUDY DESIGN: Nine chronically catheterized fetal sheep, five with an intact and four with a surgically ligated esophagus, were studied for 7 hours on 2 consecutive days. Day 1 was a control day in which the fetal parameters of arterial, venous, and amniotic fluid pressures; heart rate; and urine flow were measured continuously. Fetal and maternal blood, amniotic fluid, and fetal urine were sampled for osmolality, electrolytes, blood gases, and pH twice during the first hour and hourly thereafter. On day 2, 15 mg of furosemide was injected into the amniotic cavity after 1 hour and fetuses were monitored in the same fashion as on the control day. RESULTS: On day 2, both intact and ligated fetuses demonstrated a rapid and prolonged increase in urine flow (p < 0.01) compared with control day fetuses. Esophageal ligation decreased, but did not eliminate, the diuresis. Free water clearance increased equally (p < 0.05) in both groups compared with control fetuses. Sodium and chloride excretion increased significantly in intact (sodium 591% +/- 220% and chloride 763% +/- 295%) and ligated fetuses (sodium 234% +/- 70% and chloride 409% +/- 74%) compared with control fetuses. CONCLUSIONS: Diuresis after esophageal ligation demonstrates that furosemide is absorbed by the ovine intramembranous pathway.

Eflornithine treatment in SHR: potential role of vascular polyamines and ornithine decarboxylase in hypertension.

This study was performed to assess the potential role of polyamines in the alterations in vascular structure and function in spontaneously hypertensive rats (SHR). The effects of chronic administration of eflornithine (alpha-difluoromethylornithine; DFMO), a highly specific inhibitor of ornithine decarboxylase (the rate limiting enzyme in polyamine biosynthesis), on vascular polyamine contents, vascular structure and function, and blood pressure was studied. Male SHR (16-17 weeks of age) with an average systolic blood pressure (SBP) of 161 +/- 3 mmHg were used. The rats were divided into two groups and received either tap water or a 1% DFMO solution to drink for 6 weeks. SBP and body weight were recorded prior to and once-a-week during the experiment. Standard in vitro vascular reactivity studies on ring segments of aorta and tail artery were performed. Ring segment weight, arterial medial thickness, and vascular polyamine contents were also determined. Body weights were not significantly affected by the DFMO treatment. SBP in control SHR rose progressively to an average value of 185 +/- 5 mmHg by the sixth experimental week. Although DFMO treatment did not cause a significant decrease in SBP compared to pretreatment values, it did prevent a further increase in SBP. Aortic and tail artery responsiveness to norepinephrine and electrical stimulation, respectively, ring segment weight, arterial medial thickness, and vascular polyamine contents were all significantly less in SHR receiving the DFMO treatment. These data are the first to demonstrate the effectiveness of DFMO to lower polyamine contents in the vasculature of hypertensive SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential cerebrovascular responsiveness in spontaneously hypertensive rats following antihypertensive treatment with clonidine and verapamil.

Numerous studies have been reported examining the effects of antihypertensive treatment on peripheral vascular responsiveness in spontaneously hypertensive rats (SHR). This study was conducted to determine the effects of chronic treatment with 2 antihypertensive agents on cerebrovascular responsiveness in male SHR and Wistar-Kyoto (WKY) rats. SHR and WKY (3-4 weeks old) received either placebo, clonidine (CLON, 10 mg pellet) or verapamil (VER, 5 mg pellet). Vascular reactivity studies on the basilar artery, using standard smooth muscle bath techniques, were conducted following 6 weeks of treatment. Both CLON and VER significantly attenuated the rise in blood pressure in SHR. Basilar artery responsiveness to KCl, serotonin (5-HT), and calcium were significantly increased whereas responses to acetylcholine (ACH), isoproterenol (ISO) and sodium nitroprusside (SNP) were significantly reduced in SHR compared to WKY. CLON had no effect on basilar artery responsiveness to either the contractile or relaxation agents in SHR. However, although responses to KCl, 5-HT and calcium were not affected by VER in SHR, VER significantly increased the responses to ACH, ISO and SNP. Neither CLON nor VER treatment affected basilar artery responsiveness to any of the agents in WKY. These data demonstrate that, even though CLON and VER have similar antihypertensive effects, differential effects of the 2 agents on cerebrovascular responsiveness in the SHR are apparent. This would suggest that the vascular effects of VER and CLON are dependent upon the mechanism of action of the agents and not simply due to prevention of the elevation in blood pressure.

Chronic hypertension and vascular alterations following short-term high dietary salt intake in postweaning rats.

The chronic effects of short-term administration of a high salt diet to postweaning rats on blood pressure (BP) was studied. BP was significantly elevated following 4 weeks of treatment. After stopping the high salt diet, BP dropped to control levels but then progressively rose again to hypertensive levels. A significant increase in arterial medial thickness as well as an increase in contractile sensitivity and a decrease in relaxation responsiveness were observed in aortic smooth muscle. These data show that short-term administration of a high salt diet to normal postweaning rats results in a chronic elevation in BP accompanied by significant alterations in vascular structure and function.

Ontogeny of vascular smooth muscle responsiveness in the postweaning rat.

This study investigated the ontogeny of contractile and relaxation responses in aortic and tail artery preparations from 3-, 7-, and 11-week-old male Sprague-Dawley rats. Contractile responses to norepinephrine, serotonin, KCl, electrical stimulation, and potassium-free physiological solution were significantly increased in vascular smooth muscle from 3-week-old rats when compared to 7- and 11-week-old rats. Endothelium-dependent acetylcholine-induced relaxation and beta-adrenoceptor mediated isoproterenol-induced relaxation were significantly attenuated with maturation. These data demonstrate that significant changes occur in aortic and tail artery smooth muscle responsiveness during the postweaning maturational period of the rat. The alterations may have significant implications with regard to cardiovascular and thermoregulatory function as well as the age of the animal when utilized as an experimental model for identifying pathogenic mechanisms involved in various disease states such as hypertension. As such, further studies are warranted to determine if similar ontogenic changes in vascular function occur at the level of the resistance vessel.

Skeletal effects of calcitonin in ovariectomized rats.

Although calcitonin (CT) has been shown to be effective for the prevention of bone loss in early postmenopausal women, the skeletal effects of the hormone specifically during the early stages of estrogen deficiency have not been characterized histomorphometrically to date. The current study involves use of the ovariectomized (OVX) rat as an animal model for early postmenopausal bone loss to perform such a histomorphometric analysis. One group of OVX rats was injected sc with salmon CT on alternate days for a 6-week period. Additional groups of OVX and sham-operated control rats were treated with vehicle alone. In comparison to control rats, the proximal tibia of vehicle-treated OVX rats were characterized by a 3-fold decrease in cancellous bone volume and significant increases in osteoblast surface (+200%), osteoclast surface (+143%), mineralizing surface (+111%), mineral apposition rate (+36%), bone formation rate (+181%), and longitudinal bone growth (+38%). In contrast, treatment of OVX rats with CT normalized tibial cancellous bone volume and significantly decreased all of the above cellular- and fluorochrome-based indices of bone turnover to near control levels. The results indicate that CT treatment depresses bone turnover and prevents the development of osteopenia in OVX rats. These findings are consistent with the bone protective effect of CT in early postmenopausal women and further support the OVX rat as an animal model for the preclinical evaluation of prophylactic treatments for postmenopausal bone loss.

Polyamines, vascular smooth muscle, and deoxycorticosterone acetate-salt hypertension.

This study was performed to determine if an alteration in vascular polyamine contents is associated with the development of deoxycorticosterone acetate-salt hypertension. The effects of chronic administration of alpha-difluoromethylornithine, a specific irreversible inhibitor of ornithine decarboxylase and thus polyamine biosynthesis, on vascular polyamine contents, structure, and function as well as the development of hypertension was studied. Control and deoxycorticosterone acetate-salt rats received either tap water or a drinking solution containing alpha-difluoromethylornithine for 6 weeks, during which period systolic blood pressures were recorded. Vascular reactivity studies were performed on rings of aorta and tail artery. Medial thickness, vessel weight, and vascular polyamine contents were also assessed in these arteries. alpha-difluoromethylornithine treatment had no significant effect on either systolic blood pressure or vascular structure, function, and polyamine contents of control animals. The elevation in blood pressure and the increase in medial thickness, ring weight, and vascular polyamine contents as well as altered vascular reactivity observed in deoxycorticosterone acetate-salt rats was significantly attenuated by alpha-difluoromethylornithine treatment. These results are the first to demonstrate that vascular polyamine contents are elevated in the deoxycorticosterone acetate-salt rat and that chronic alpha-difluoromethylornithine treatment prevents the rise in vascular polyamines as well as the elevation in blood pressure and attendant changes in the vasculature. Thus, the increase in vascular polyamines may comprise a critical link between the initiating stimuli and the alterations in vascular structure and function implicated in the pathogenesis of deoxycorticosterone acetate-salt hypertension.

Age-dependent salt-induced hypertension in the rat: prevention with DSP-4, a selective noradrenergic neurotoxin.

The present study was performed to determine if chronic administration of a high salt diet induces hypertension similarly in young and adult rats and if treatment with DSP-4 alters the development of the hypertension. Three- (young) and ten- (adult) week-old male Sprague-Dawley rats were fed either a standard rat chow diet (0.71% NaCl), a 4% NaCl diet or an 8% NaCl diet for 12 weeks. Systolic blood pressure, using a standard tail-cuff technique, and body weight were recorded weekly during the dietary treatment period. Direct mean arterial pressure, heart rate, heart weight and kidney weight were determined after 12 weeks. Body weight was slightly reduced in young rats on the 8% NaCl diet. A significant increase in blood pressure as well as heart weight was observed only in young rats on the 8% NaCl diet. An increase in kidney weight was observed in both young and adult rats on the 8% NaCl diet. DSP-4 treatment prevented the development of hypertension as well as cardiac hypertrophy in rats fed the high salt diet but had no effect on rats receiving the normal diet. Body and kidney weights were similar in vehicle- and DSP-4-treated rats on the 8% NaCl diet. These results demonstrate that a critical developmental/maturational period exists during which the young rat is susceptible to the hypertensinogenic effects of a high salt diet. An intact central noradrenergic system appears to be necessary for the expression of this enhanced susceptibility and the subsequent development of hypertension.

Incidence of postoperative infection in a free-standing ambulatory surgery center.

A 1-year study was undertaken at the Hugar Surgery Center, a freestanding ambulatory surgery center, to determine the infection rate for outpatient podiatric surgery. One hundred and forty-eight patients underwent foot surgery that included digital, soft tissue, metatarsal, simple bunionectomies, complex hallux abducto valgus correction with osteotomy and internal fixation, first metatarsophalangeal joint implant arthroplasty, midfoot, and rearfoot procedures. An infection rate of 1.35% was identified. The study indicates all types of podiatric surgery may be performed at ambulatory surgery centers without increased risk of postoperative infection. Infection rate of 1.35% is quite acceptable for clean foot surgery and compares rather favorably with hospital infection rates.

The effects of the inverse bevel flap procedure on gingival contour and plaque accumulation.

Periodontal surgery should eliminate disease and produce a good gingival contour to allow ease of cleaning and maintenance. An important factor in the achievement of these aims may be the contour of the attached gingiva following surgery. At present, gingival contour is evaluated by one of two indices. A new disease-related gingival contour index was designed and compared with existing indices (plaque index, periodontal index, sulcus bleeding index) following inverse bevel flap procedures. The results demonstrated that there was a statistically significant increase in the scores for gingival contour (p less than 0.001) a significant decrease in scores for the periodontal index (p less than 0.001) and sulcus bleeding index (p less than 0.05), but no change in the amounts of plaque accumulating (p greater than 0.7).

Comparison of hypertonic saline and chlorhexidine mouthrinses after the inverse bevel flap procedure.

THE VALUE OF periodontal dressings after periodontal surgery has been questioned. This study further evaluated chlorhexidine as a possible alternative. A group of nine patients requiring comparable bilateral inverse bevel flap procedures underwent preoperative oral hygiene instruction and scaling. Immediately before surgery and up to 3 months postoperatively, clinical records of plaque index, pocket depths and sulcus bleeding index were made. Records were taken of patients' postoperative discomfort and preferences. During the 1st postoperative week either a 0.2% chlorhexidine gluconate or a 1% saline mouthrinse was prescribed. Plaque accumulation and sulcus bleeding were significantly reduced on the sides treated with chlorhexidine. Significant reductions in pocket depths were recorded for both groups but there were not differences between treatments. Less postoperative discomfort was experienced with chlorhexidine, although the difference was not significant. Five patients preferred chlorhexidine, one saline, and three had no preferences. These and previous results suggest that a periodontal dressing is unnecessary or even undesirable after the inverse bevel flap procedure, and may be usefully replaced by a suitable antiplaque agent.

A comparison of a periodontal dressing and chlorhexidine gluconate mouthwash after the internal bevelled flap procedure.

A group of 15 patients requiring comparable bilateral internal bevelled flap procedures took part in a study to compare the clinical results achieved when a dressing or chlorhexidine mouthwash was used during the first postoperative week. Initial preoperative conditions were comparable. At the end of the first postoperative week, significantly more plaque accumulated and the sulcus bleeding index was significantly higher on the dressing treated side. At 1 month and 3 months postoperatively the sulcus bleeding indices were below preoperative levels for both treated sides with no significant differences between the sides. A significant and comparable reduction in pocket depths occurred following the two postoperative treatments. Subjectively recorded pain scores demonstrated that more pain was experienced on the dressing treated side, particularly during the first 4 postoperative days. More patients preferred the mouthwash as a postoperative treatment.