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Biomedical subjects

R P White

Publications and source records attributed to R P White.

At least 19 recordsLinked to original sources
PubMed1992

Stability of surgical maxillary expansion.

Stability after transverse expansion of the maxilla via Le Fort I osteotomy with segments was evaluated in 39 patients. The average expansion was 5.4 mm at the second molars, decreasing almost linearly to 2.8 mm at the first premolars. Postsurgical relapse also was greatest at the second molars, averaging 2.6 mm. The percentage of relapse was greatest posteriorly, decreasing from 49% at the second molars to 30% at the first premolars. Considerable variability in stability followed surgery: Three-fourths of the patients had some relapse at the first molars (greater than 3 mm in 28%), but one fourth were stable. Sixty-two percent of the patients had a net posttreatment gain in arch width at the first molars. No correlation was found between transverse relapse and the type of presurgical orthodontic tooth movement, the use of rigid fixation, or the use of an auxiliary stabilizing arch wire. The amount of postsurgical relapse was significantly greater in those who had concurrent mandibular surgery. To improve clinical results with surgical expansion, we recommend (1) moderate overexpansion at surgery for major transverse changes, (2) maintenance of the occlusal splint for at least 6 weeks, and (3) use of a lingual arch wire or auxiliary labial arch wire to maintain molar width during postsurgical orthodontics.

Adult↗
PubMed1992

Recovery following orthognathic surgery and autologous blood transfusion.

Patients undergoing maxillary surgery, with or without mandibular surgery, were divided into two groups. One surgeon's patients served as controls and did not receive blood unless hemodynamically indicated. The remaining surgeons' patients were transfused regardless of their hemoglobin levels following surgery. An attempt was made to identify benefits or complications associated with the reinfusion of autologous blood, particularly in patients with "low blood loss." Patients were asked to record when they returned to their presurgical level of activity. Of the 46 patients in the study 14 (12 nontransfused, two transfused) were not back to full activity 6 weeks after surgery. Of the 32 patients that reported a return to full activity within the study period, transfused patients reported a significantly quicker return to full activity at 2 weeks, 3 weeks, and 4 weeks postoperatively than did their nontransfused counterparts, even when blood loss at surgery was minimal. No complications have occurred with this practice.

Adolescent↗
PubMed1991

Capric acid as a potent dilator of canine vessels in vitro and in vivo.

1. Pharmacodynamic effects of even numbered saturated fatty acids, C4-C16, were determined on isolated canine basilar and femoral arteries precontracted with PGF2 alpha. 2. The fatty acids relaxed the precontracted vessels. 3. The basilar artery was the most sensitive vessel and caprate (C10) was the most potent acid with an EC50 of 49 microM. 4. The relaxant effect was endothelium-independent. 5. Contractions elicited by norepinephrine, serotonin, and U46619 were also inhibited. 6. Caprate (C10) given intra-arterially increased femoral blood flow in a dose-dependent manner and the dose computed to increase blood flow 50% was 1.27 microM/kg.

Animals↗
PubMed1991

Identification of capric acid as a potent vasorelaxant of human basilar arteries.

To determine whether naturally occurring fatty acids, especially saturated ones, might act directly as vasodilators, segments of human basilar arteries and umbilical arteries were precontracted submaximally with prostaglandin F2 alpha and then exposed to different saturated fatty acids (C4 through C16) or unsaturated fatty acids (C14:1, C18:1, C18:2, and C18:3) at concentrations from 4 microM to 4 mM. The results showed caprate (C10) to be the most potent vasorelaxant and basilar arteries to be more responsive (EC50 = 63 microM) than umbilical arteries (EC50 = 780 microM). Caprate also inhibited contractions elicited by KCl, serotonin, and the thromboxane analogue U46619. The relaxation was independent of the endothelium, and potency was not related to the weak capacity of caprate to inhibit Ca(2+)-induced contractions of K(+)-depolarized basilar arteries. The pattern of potencies for the arteries differed, but among unsaturated fatty acids the monounsaturated (C14:1, C18:1) were more potent than the polyunsaturated (C18:2, C18:3). Comparing the potencies obtained with the concentrations reported for the free fatty acid content of arteries, brain, and plasma indicates that these lipids could influence vasomotion in health and disease.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Intracoronal radiolucencies within unerupted teeth. Case report and review of literature.

A panoramic radiograph obtained during orthodontic treatment revealed an intracoronal radiolucency within an unerupted permanent second molar. This unusual entity was successfully treated by surgical and endodontic intervention, followed by restorative and orthodontic treatment. These treatments enabled the tooth to maintain pulpal vitality, erupt, complete root formation, and function. This report will review the proposed etiologies for this condition, discuss the need for surgical intervention, and present the details of the case.

Calcium Hydroxide↗
PubMed1990

Eicosanoid levels in CSF of premature infants with posthemorrhagic hydrocephalus.

The cerebrospinal fluid (CSF) of 11 premature infants suffering from posthemorrhagic hydrocephalus was examined by radioimmunoassay for prostaglandin (PG) E2, PGF2 alpha, PGD2, 6-keto PGF1 alpha, thromboxane B2 (TxB2) and peptidoleukotrienes (LTC4/LTD4). The LTs were detected in the CSF of more of these patients (70%) than any of the other eicosanoids, and usually in the highest concentration. Among the 11 posthemorrhagic patients CSF eicosanoid levels were highest when determined soon after injury. Moreover, the variety of eicosanoids present, as well as concentrations, in these infants decreased with time. The types of eicosanoids most evident in the CSF of patients who required shunting were TxB2 and LTs, being present together in 5 of 6 (83%) of these infants. In contrast, 1 of 5 (20%) of the patients who did not require this neurosurgical intervention contained both TxB2 and LTs, the remaining having only one or neither eicosanoid. The highest average concentration for each eicosanoid studied was (pg/ml): PGE2, 628; PGF2 alpha, 985; PGD2, 1410; 6-keto PGF1 alpha, 544; TxB2, 486 and LTs, 1229. This study is the first to demonstrate that the CSF of preterm infants may contain a wide variety of eicosanoids and indicates that these lipids are a manifestation of neurological assault.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Who needs surgical-orthodontic treatment?

The indication for surgical-orthodontic treatment is a skeletal or dentoalveolar deformity so severe that the magnitude of the problem lies outside the envelope of possible correction by orthodontics alone. For adults, this means that satisfactory correction by tooth movement is not possible; for children, it means that the problem cannot be corrected satisfactorily by a combination of tooth movement and growth modification. Correction of the dental occlusion is not an adequate description of successful treatment; satisfactory facial esthetics must also result. Extrapolation from existing data for malocclusion in the United States suggests that there are a total of 1.2 million individuals in the present population with problems severe enough to require surgical-orthodontic treatment for satisfactory correction. Of these, 700,000 have Class II malocclusions and 300,000 have Class III malocclusions. Approximately 220,000 individuals have long-face problems and another 220,000 have other problems, but these groups have about a 60% overlap with the Class II and Class III groups.

Adolescent↗
PubMed1990

Responses of isolated cerebral arteries to vasoactive agents.

One hypothesis of cerebral vasospasm contends that the slow onset and eventual disappearance of the spasm of subarachnoid hemorrhage is caused by the finite production of spasmogens. These are generated and accumulate in the basal cisterns as the result of chemical reactions between blood elements, arterial wall, leptomeninges, and brain. The spasmogens may spread in the general direction of bulk CSF flow to affect arteries more distally. Pharmacodynamic studies performed on isolated cerebral arteries show that a vast array of naturally occurring substances are vasoactive. Among these, derivatives of arachidonate (eicosanoids) are strong candidates as spasmogens because they produce strong, prolonged contractions in human arteries and because the CSF levels of some eicosanoids are preferentially elevated in subarachnoid hemorrhage patients who experience severe spasm. The spasm may be largely refractory to treatment because the intravasation of blood elements and the coagulum serve as barriers to therapeutic agents and because cerebral arteries are devoid of vasa vasorum; however, in animal models of chronic subarachnoid hemorrhage, calcium antagonists given intrathecally will reverse the spasm. Other therapeutic strategems are being tried experimentally and clinically, including compounds like prostacyclin that relax cerebral arteries and inhibit platelets. In vitro studies indicate further that some plasma proteins (e.g., haptoglobin, antithrombin III) and several products of endothelial synthesis (PGI2, EDRF) may naturally provide protection against the genesis of vasospasm. The in vitro responses to bloody CSF are capricious but are not due to many pharmacologically defined substances, including hemoglobin. Hemoglobin and its derivatives, however, may be critical to the enhanced lipid peroxidation and free-radical production that occur in subarachnoid hemorrhage.

Animals↗
PubMed1989

Pharmacodynamic study of maturation and closure of human umbilical arteries.

The contractile effects of 19 factors on isolated human arterial segments at term pregnancy were quantified, and 14 contractile agents were similarly applied to preterm (23 to 35 weeks) umbilical arteries. Responses to potassium chloride were used to normalize the data. At comparison with the term vessel, the preterm artery contracted more to angiotensin II and arachidonic acid and was more sensitive to oxytocin. Contractions were greater in term arteries to vasopressin, norepinephrine, prostaglandin D2, and prostaglandin E2 but similar in both group of arteries to bradykinin, histamine, acetylcholine, and prostaglandin F2 alpha. Neuropeptide Y, linoleic acid, uridine triphosphate, and thrombin were ineffective. Hyperoxia inconsistently induced weak, short-lived contractions. Contractions to cooling manifested marked desensitization and tachyphylaxis. Serotonin was the only agonist that displayed the pharmacodynamic features most likely to be important for closure: potency, efficacy, and long duration of action (greater than 2.5 hours). It was postulated that cellular elements surrounding umbilical vessels are primary sources of vasoactive agents that are important to closure of the fetoplacental circulation at birth.

Amines↗
PubMed1989

A peripheral giant-cell granuloma manifestation of primary hyperparathyroidism: report of case.

Profuse granulomatous masses of the gingiva frequently occur in patients with gingival and periodontal disease. A 33-year-old female was seen for followup of a previously treated peripheral giant-cell granuloma. Two years earlier, a mass had been removed from the gingiva between the maxillary right central and lateral incisors. Current laboratory test results indicated hyperparathyroidism, and led to the discovery of a parathyroid adenoma. After the gingival lesion, adjacent teeth, and parathyroid adenoma were removed, the patient had no further recurrence of the lesion or signs of hyperparathyroidism.

Adenoma↗
PubMed1989

Complications of orthognathic surgery: a comparison between wire fixation and rigid internal fixation.

This retrospective review compares the results of using rigid internal fixation (RIF) and wire fixation for orthognathic surgery patients. The records of two groups of demographically similar patients who underwent comparable surgery, performed by the same four attending surgeons at the same institutions during the same time period (1983 to 1986), were evaluated for complications and unanticipated treatment results. The most striking finding of this study is the general similarity between the two groups. However, differences in frequency of excessive weight loss and persistent restriction of mandibular opening suggest a benefit from early mobility of the mandible that comes with RIF. Because there was no concomitant increase in complications or unexpected results of treatment, the introduction of RIF for orthognathic surgery may offer patients some potential advantages.

Humans↗
PubMed1988

Comparison of vasorelaxants in human basilar arteries and umbilical arteries.

The vasodilatation produced by adenosine, sodium nitrite, and papaverine was compared on isolated human basilar arteries and umbilical arteries precontracted with 30 mM KCl or submaximal concentrations of serotonin and prostaglandin F2 alpha. The basilar artery was far more sensitive to the vasodilators than the umbilical vessel. Papaverine, for instance, was 133 times more effective (EC50 = 3.9 x 10(-6) M) in basilar arteries precontracted with KCl than it was in the umbilical artery (EC50 = 5.2 x 10(-4) M) and all dilators inhibited by at least 95% basilar arteries precontracted with serotonin or prostaglandin F2 alpha. In contrast, umbilical arteries precontracted with KCl or prostaglandin F2 alpha failed to relax significantly to adenosine and sodium nitrite at concentrations that exceeded 10(-3) M, and contractions elicited by serotonin were inhibited by less than 40%. The results support the concept that physiological mechanisms responsible for dilation in most vessels are deficient in the umbilical artery and that the deficiency may be related to the role this atypical vessel plays in closure of the extracorporeal circulation at birth.

Basilar Artery↗
PubMed1988

Pharmacodynamic effects of tosyl-arginine methyl ester (TAME) on isolated human arteries.

1. The effects of the competitive proteinase inhibitor TAME on isolated human umbilical and basilar arteries were studied. 2. Most experiments were performed on umbilical arteries and showed that 5 x 10(-4) M or 5 x 10(-3) M TAME significantly inhibited contractions elicited by prostaglandin F2 alpha, bradykinin, serotonin, and histamine. The inhibition was not endothelium-dependent. 3. The contraction elicited by prostaglandin E2 in basilar arteries was inhibited by TAME in a dose-dependent manner indicating that inhibition did not depend on the origin of the vessel. 4. Inhibition by 5 x 10(-7) M TAME of the contraction produced by KCl in the basilar artery was limited to low concentrations of KCl (10 and 30 mM). TAME did not significantly inhibit contractions of umbilical arteries to KCl. 5. At 5 U/ml (approximately 8.6 x 10(-8) M) antithrombin III markedly inhibited contractions of basilar arteries to prostaglandin E2 but had no effect of contractions elicited by 10(-6) M serotonin in the umbilical artery, nor did aprotinin (5 x 10(-4) M). 6. Although vessels of different origin may differ in sensitivity, the manifest effect of antiproteinases on arteries is inhibition.

Antithrombin III↗
PubMed1987

Responses of human basilar arteries to vasoactive intestinal polypeptide.

The responses to 9 X 10(-7) M vasoactive intestinal polypeptide (VIP) by isolated human basilar arteries of 30 individuals were studied to further elucidate the role the peptide might play in modifying cerebrovascular tone normally and in disease. In most experiments the artery was precontracted with prostaglandin F2 alpha (PGF2 alpha), either with 1 or 2 X 10(-6) M or with 10(-5) M PGF2 alpha. The course of action to VIP was observed for 15 min following its application to the contracted vessel. Some arteries failed to respond to VIP (13%), otherwise the arteries relaxed 44% when the contraction was induced by 10(-5) M PGF2 alpha and 67.6% after the lower concentrations of PGF2 alpha. There was no significant decrement in the vasorelaxant effect of VIP throughout the period of observation. A second and third application of VIP to the precontracted artery produced significantly less of an effect than the first, but no consistent progressive pattern of tachyphylaxis was evident. In additional experiments, indomethacin (10(-5) M) did not prevent the vasorelaxant effect of VIP, suggesting that prostanoid synthesis was not involved. Pretreatment of the artery with VIP did not prevent the contractions generated by 10, 30, 50 and 90 mM KCl while antithrombin III (1.2 X 10(-7) M) did, indicating fundamental differences between these two vasorelaxants. In conclusion, VIP will inhibit contraction of isolated human cerebral arteries for prolong periods and could be a significant factor regulating cerebral blood flow in humans.

Antithrombin III↗
PubMed1987

Comparison of the inhibitory effects of antithrombin III, alpha 2-macroglobulin, and thrombin in human basilar arteries: relevance to cerebral vasospasm.

Isolated human basilar arteries were used in this study to evaluate the inhibitory effect of antithrombin III (AT III), thrombin, and alpha 2-macroglobulin (alpha 2-M) on contractions elicited by K+, serotonin (5-HT), prostaglandin (PG) D2, PGF2 alpha, and plasmin. alpha 2-M (0.5-1.0 mg/ml) failed to affect the contractions produced by contractile agonists significantly but did notably reduce the basal tone of the arteries. Thrombin (1 and 10 U/ml) reduced basal tone and significantly inhibited the contractions elicited by K+, PGF2 alpha, and plasmin. The relaxant effect of thrombin was abolished by procedures that destroy endothelium and by exposing the artery to thrombin for prolonged periods (tachyphylaxis). AT III (1-6 U/ml) reduced basal tone and significantly inhibited, in a concentration-dependent manner, the contractile responses to K+, 5-HT, PGD2, PGF2 alpha, and plasmin. In sharp contrast to thrombin, AT III did not induce tachyphylaxis nor was its vasorelaxant effect significantly reduced by destruction of the endothelium. The results show AT III to be a potent and nonspecific inhibitor of human cerebral arteries and support the hypothesis that AT III may contribute to the delay of cerebral vasospasm seen in patients who experience aneurysmal hemorrhage.

Adolescent↗