Impact of magnetic resonance imaging on the surgical management of cystic hygromas

BACKGROUND

The surgical management of cystic hygromas can be challenging, and accurate diagnosis and anatomic localization is essential. The literature on the use of magnetic resonance imaging (MRI) in pediatric cystic hygromas is sparse and mostly limited to radiological descriptions.

METHODS

The authors present five cases of cystic hygromas in children ranging in age from 1 to 13 years. The preoperative MRI scans and patient charts were reviewed with attention to the clinical, radiological, surgical, and histological findings.

RESULTS

MRI produced highly detailed multiplanar renderings of the cystic hygromas that were both diagnostic and predictive of the subsequent intraoperative findings. This modality helped specifically in some cases to identify lesion extensions that required specific surgical attention. There were no recurrences or complications at a mean follow-up of 18 months.

CONCLUSION

The use of MRI in cystic hygromas can facilitate accurate diagnosis and assist in the preoperative planning, thereby contributing to the successful treatment of these lesions.

Sequence variation and phylogenetic analysis of envelope glycoprotein of hepatitis G virus

A transfusion-transmissible agent provisionally designated hepatitis G virus (HGV) was recently identified. In this study, we examined the variability of the HGV genome by analysing sequences in the putative envelope region from 72 isolates obtained from diverse geographical sources. The 1561 nucleotide sequence of the E1/E2/NS2a region of HGV was determined from 12 isolates, and compared with three published sequences. The most variability was observed in 400 nucleotides at the N terminus of E2. We next analysed this 400 nucleotide envelope variable region (EV) from an additional 60 HGV isolates. This sequence varied considerably among the 75 isolates, with overall identity ranging from 79.3% to 99.5% at the nucleotide level, and from 83.5% to 100% at the amino acid level. However, hypervariable regions were not identified. Phylogenetic analyses indicated that the 75 HGV isolates belong to a single genotype. A single-tier distribution of evolutionary distances was observed among the 15 E1/E2/NS2a sequences and the 75 EV sequences. In contrast, 11 isolates of HCV were analysed and showed a three-tiered distribution, representing genotypes, subtypes, and isolates. The 75 isolates of HGV fell into four clusters on the phylogenetic tree. Tight geographical clustering was observed among the HGV isolates from Japan and Korea.

The association of squamous cell carcinomas of the nasopharynx with Epstein-Barr virus shows geographical variation reminiscent of Burkitt's lymphoma

Nasopharyngeal carcinoma (NPC) is rare in most parts of the world but occurs with high incidence in certain regions, such as South-East Asia. Two major histological types of NPC are recognized, non-keratinizing carcinoma and squamous cell carcinoma. Non-keratinizing NPCs, which include undifferentiated NPC, are invariably associated with Epstein-Barr virus (EBV) infection, regardless of the geographical or ethnic origin of the patients. By contrast, conflicting results have been published concerning a possible association of squamous cell NPC with the virus. To address this question, squamous cell NPCs have been collated from an area where NPC is endemic, Hong Kong, and from two regions where NPC occurs with a lower incidence, Chengdu, PR China, and Birmingham, United Kingdom. In situ hybridization for the detection of the small EBV-encoded nuclear RNAs (EBERs) demonstrated that all 22 cases from Hong Kong were EBV-positive. By contrast, EBV was detectable in 7 of 19 cases from central China, and in 3 of 7 cases from the U.K. Expression of the virus-encoded latent membrane protein 1 (LMP1) was detected in 3 of 32 EBV-positive squamous cell NPCs. These results indicate that the association of squamous cell NPCs with EBV shows geographical variability in a manner which is reminiscent of the situation encountered in Burkitt's lymphoma. This suggests that squamous cell NPCs are a pathogenetically heterogeneous group of tumours distinct from non-keratinizing NPCs.

Sequence variation and phylogenetic analysis of the 5' terminus of hepatitis G virus

We determined the nucleotide and deduced amino acid sequence of the 5' terminus of the hepatitis G virus (HGV) genome from isolates of varied geographical origins. Our analysis showed that the putative 5' non-coding region (NCR) contains several blocks of highly conserved sequences that may be useful for the development of a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for detection of HGV RNA. Overall, the degree of conservation within the 669-nucleotide (nt) 5'terminal sequence was found to range from 99.5% to 86% sequence identity. We also showed that the HGV NCR from some isolates contained conserved insertions or deletions that altered the translational reading frames at the 5'-end of the genome, resulting in different sizes of predicted polyproteins encoded by genomes of individual isolates. Specifically, the insertions/deletions affected the size of the peptide preceding the putative first envelope (E1) protein. Phylogenetic analysis of the nucleotide sequences suggested that the isolates examined can be classified into distinct groups that may be useful for studying the molecular evolution of HGV and possible relationships between isolate sequence characteristics and infection patterns.

Particle repositioning maneuver: effective treatment for benign paroxysmal positional vertigo

OBJECTIVE

To assess short-term and long-term outcomes of the particle repositioning maneuver (PRM).

DESIGN

This is a prospective study of 68 cases of benign paroxysmal positional vertigo (BPPV) in 65 consecutive patients.

RESULTS

Initially, 57 (83.8%) cases had no evidence of residual symptoms, 10 (14.7%) had a partial improvement, and only 1 (1.5%) failed treatment. In the long-term (18.7 month mean follow-up period), 43 (67.2%) cases had no history of recurrence, and 22 (34.4%) cases had recurrences, of which 14 (21.9%) experienced only mild symptoms, and 8 (12.5%) were no better than before the PRM. Of the eight who were no better, five had repeat PRMs that successfully relieved their symptoms. The final overall outcome was that 59 (95.2%) patients had either mild symptoms or no symptoms, and 3 (4.8%) patients were treatment failures. Factors that did not seem to be predictive of outcome were secondary nystagmus, gender, and duration of symptoms. In both the short and long terms, the self-limited form of BPPV was found to have the best outcome, the episodic type had an intermediate outcome, and the prolonged type had the worst outcome.

CONCLUSIONS

We postulate that outcomes are best in those cases where free-floating canaliths are the mechanism of disease, which includes patients with self-limited BPPV. Patients with episodic or prolonged BPPV may have varying degrees of underlying cupulolithiasis that cannot be entirely corrected with PRM alone.

Arachidonic acid release: an in vitro alternative for dermal irritancy testing

Validated in vitro alternatives are being utilized extensively for mutagenicity and ocular irritancy testing. However, validation of alternative assays for dermal irritancy is progressing more slowly. As the irritant response in human skin is mediated, at least in part, by eicosanoids derived from arachidonic acid, the effect of relatively pure anionic surfactants (AS, n=8) and surfactant-containing finished products (FP, n=25) on the release of [3H]arachidonic acid from a prelabelled murine fibroblast cell line (C3H-10T1/2 cells) in vitro was examined. Test substances were administered at various non-lethal concentrations, in triplicate, to 12- and 24-well plates containing preconfluent monolayers (80-90% confluence) of C3H-10T1/2 cells. Because it is impossible to test all concentrations of each test substance in a single assay, statistical techniques were developed to 'standardize' in vitro assay results. In each assay, radiolabel release due to a positive control was also measured, using 0.04, 0.05 and 0.06 mM concentrations of sodium dodecyl sulfate (SDS). Test substance releases were then transformed into 'SDS equivalent' responses, significantly reducing both inter- and intra-assay variability. A straight line was fitted to the test substance responses and compared with that for SDS to calculate the relative potency in vitro for individual AS and FP. Relative potencies correlated with in vivo responses, that is primary dermal irritation indices obtained in rabbits, with Spearman p=0.408 (P<0.03) for 32 tested agents, and p=0.976 (P<0.001) for the eight AS. Exclusion of extremely alkaline or acidic FP (pH>11 or <2, n=4) and those which were insoluble in the aqueous cell culture media at the 1% stock dilution (n=5), improved the overall in vivo-in vitro correlation significantly (p=0.683, P<0.001, n=23) and produced a significant correlation for FP alone (p=0.539, P<0.05, n=15). These results suggest that release of [3H]arachidonic acid from cultured skin cells represents a novel, mechanistically based in vitro screen for dermal irritancy testing.

Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent

An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.

Hydrolysis of N-formylmethionyl chemotactic peptides by endopeptidase 24.11 and endopeptidase 24.15

Endopeptidase 24.11 (EP 24.11), a membrane-bound cell surface enzyme, modulates chemotactic responsiveness of neutrophils to f-Met-Leu-Phe. It is unknown if the enzyme degrades potent formylmethionyl tetrapeptides or if an enzyme with similar activities, endopeptidase 24.15 (EP 24.15), degrades formylated chemotactic peptides. In a study of five formylmethionyl tetrapeptides and f-Met-Leu-Phe, we found that EP 24.11 had high affinity for all peptides evaluated, although it did not effectively degrade f-Met-Ile-Leu-Phe. EP 24.15 had high affinity for three of the tetrapeptides, and for f-Met-Leu-Phe, although, for unclear reasons, it did not degrade f-Met-Ile-Leu-Phe or f-Met-Leu-Phe, the apparent natural products of Staphylococcus aureus and Escherichia coli, respectively.

Development of a computer program for teaching periodontal diagnosis based on clinical epidemiological principles

Multimedia teaching tools in dental education are still rare. This paper describes the development of an inexpensive yet powerful computer program for instruction in the principles of clinical epidemiology. The application was developed in the context of periodontal diagnostic methodologies at the third year D.D.S. level. Principles of probabilistic thinking are invoked as the student is guided from the application of raw research data to the derivation of likelihood ratios and how they affect clinical decision making. A questionnaire was used to evaluate student satisfaction with the program and the responses indicated good acceptance of the concepts presented in the program and an interest in further computer-aided instruction.

Lowering patient dose on single-phase X-ray units

In this study, entrance skin doses for AP pelvis and lateral lumbar spine examinations were measured with single-phase, three-phase and medium frequency x-ray generators. Results showed that for equal tube voltage (kVp) exposure to achieve similar film density, the ESD was significantly higher with the single-phase generator than the other two generators. Further research showed that by increasing kVp, the single-phase generator could achieve the lower ESD values obtained with the three-phase and medium frequency generators while maintaining similar film density and contrast.

The VMH-dietary obese rat: a new model of non-insulin-dependent diabetes mellitus

A model of non-insulin-dependent diabetes mellitus (NIDDM) has been developed in adult rats by combining bilateral electrolytic lesions of the ventromedial hypothalamus (VMH) and high fat-high sucrose diets. VMH-dietary obese rats showed fasting hyperinsulinemia (> or = 540 pM) and hypertriglyceridemia (> or = 180 mg/dl) generally within 3 wk on the protocol. Fasting hyperglycemia (> or = 10 mM) was observed in the majority of animals in seven consecutive experiments. Hyperglycemic animals showed impaired glucose tolerance despite high prevailing insulin levels. Pancreatic islets isolated from VMH-dietary obese rats showed a loss of insulin secretory response to glucose by week 5, before the onset of hyperglycemia. Islets from hyperglycemic rats no longer responded to an increase in glucose concentration and failed to suppress insulin release normally in response to 15 nM norepinephrine or to a decrease in glucose concentration. This model mimics the major characteristics of obesity-associated human NIDDM as well as several stages of its progression, rendering it useful for studying the etiology of the metabolic and secretory defects in the syndrome.

Effect of respiratory acidosis and alkalosis on plasma catecholamine concentrations in anaesthetized man

1. Plasma concentrations of noradrenaline and adrenaline were measured in 11 anaesthetized patients during normocapnia, hypocapnia and hypercapnia. Hypocapnia was produced by deliberate hyperventilation and hypercapnia by adding carbon dioxide to the inspired gas mixture. 2. With a median (range) arterial partial pressure of carbon dioxide of 4.7 (4.2-5.2) kPa, the median (range) plasma concentration of noradrenaline was 0.41 (0.12-0.94) nmol/l and of adrenaline was 0.15 (0.05-0.31) nmol/l. 3. With an arterial partial pressure of carbon dioxide of 2.6 (2.2-3.3) kPa, there was no change in the plasma concentration of noradrenaline [0.37 (0.12-0.86) nmol/l] or that of adrenaline [0.16 (0.05-0.32) nmol/l]. 4. However, with an arterial partial pressure of carbon dioxide of 10.4 (7.6-13.2) kPa, there were significant increases in the plasma concentrations of both noradrenaline [1.13 (0.79-2.05) nmol/l, P < 0.01] and adrenaline [0.67 (0.20-2.92) nmol/l, P < 0.05]. 5. This is the first demonstration in man that respiratory acidosis causes an increase in plasma concentrations of catecholamines.

Identification of two zinc metalloendopeptidases in alveolar macrophages of rats, guinea pigs, and human beings

Neutral endopeptidases EC 3.4.24.11 and EC 3.4.24.15, widely distributed zinc metalloendopeptidases, degrade a number of biologically active peptides including substance P, bradykinin, neurotensin, and luteinizing hormone-releasing hormone. In this study we measured EC 3.4.24.11 and EC 3.4.24.15 activity in alveolar macrophages, key inflammatory cells in the lung that produce and respond to a large number of bioactive substances including chemotactic peptides, with the substrates glutaryl-ala-ala-phe-2-naphthylamide and tertiary butoxycarbonyl-phe-ala-ala-phe-paraaminobenzoate, respectively. We found that specific activity of EC 3.4.24.15, defined as activity inhibited with N-[(1RS)-carboxy-3-phenylpropyl]-ala-ala-phe-paraaminobenzoate+ ++, was significantly higher (p < 0.001) in cells from Sprague-Dawley rats (485 +/- 123 nmol/mg protein.hr) than in cells from Hartley guinea pigs (138 +/- 94 nmol/mg protein.hr), healthy human male smokers (121 +/- 73 nmol/mg protein.hr) and healthy human male nonsmokers (94 +/- 12). In contrast, activity of EC 3.4.24.11, defined as activity inhibited with N-[(1RS)-carboxy-3-phenylpropyl]-phe-paraaminobenzoate, was significantly higher (p < 0.001) in cells from human smokers (689 +/- 167 nmol/mg protein.hr) and nonsmokers (762 +/- 136 nmol/mg protein.hr) than in cells from rats (52 +/- 12 nmol/mg protein.hr) and guinea pigs (34 +/- 14 nmol/mg protein.hr). An additional activity in alveolar macrophages toward tertiary butorycarbonyl-phe-ala-ala-phe-paraaminobenzoate was inhibited with L-3-carboxy-trans-2,3-epoxypropionyl-leucylamido-(4-guanido) butane, a specific inhibitor of cysteine proteinases, a finding of interest because in general enzymes in this class show little activity at neutral pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Empirical assessment of the effect of different summary worklife exposure measures on the estimation of risk in case-referent studies of occupational cancer

The effect of different summary measures of worklife exposure on the estimation of risk is reported. Two matched case-referent studies associating sulfuric acid exposure and cancer from Baton Rouge and southern Ontario were used. Five summary exposure measures were converted to discrete levels of exposure through the selection of equivalent percentile points on each measure's respective percentage frequency distribution for logistic regression modeling purposes. The southern Ontario data set exhibited only minor differences across all five exposure measures. The Baton Rouge data set, however, produced different results, and the time-dependent measures appeared to underestimate risk. It is possible, therefore, to obtain different estimates of risk depending on the exposure measure selected. It is recommended that, in the absence of proved models for assessing exposure, a variety of summary measures be used to estimate risk. This approach would facilitate the comparison of findings across studies.

Comparison of self-instruction methods for teaching diagnostic testing

In a randomized controlled trial, self-teaching booklets and computer media were evaluated for teaching diagnostic testing to dental students as a foundation for further development of clinical decision making skills. Effectiveness was assessed by pre- and post-tests. Reliability of these test instruments was examined by analyzing the pre- and post-test scores of 49 first year dental students who received no instruction. Forty-one second year dental students were exposed to clinical epidemiological principles applied to endodontic diagnosis through either self-teaching booklets or computer media. No statistically significant difference was found between the mean test scores of the students through self-teaching booklets and computer media. Although first and second year students showed a statistically significant improvement between the pre-test and post-test, the improvement in the second year class was greater. An addendum was later made to the main trial to compare the self-teaching booklet to the traditional lecture format in teaching endodontic diagnosis. Seventy-one third year dental students were exposed to these same materials through either a lecture or the self-teaching booklet and then similarly tested. There was no significant difference between the self-teaching booklet and traditional lecture for the third year students.

Recognition of a peroxisomal tripeptide entry signal by the glycosomes of Trypanosoma brucei

Trypanosomes compartmentalise the first 9 enzymes of glycolysis and glycerol metabolism in peroxisome-like microbodies known as glycosomes. The identity of the sequences that direct proteins into the glycosome has until now been uncertain. We show here that the peroxisomal tripeptide entry signal is sufficient to cause association of a bacterial enzyme with the glycosomes of Trypanosoma brucei. However, it works less efficiently than the C-terminal 21 amino acids of trypanosome glycosomal phosphoglycerate kinase.

Recovery of malignant tumor cells from the right atrium during hepatic resection for hepatocellular carcinoma

Tumor cells were recovered from the right atrium in three of five patients during hepatic resection for hepatocellular carcinoma. Mechanical factors during blunt mobilization and rotation of the hepatic tumor appeared to be responsible for tumor dislodgement into the venous circulation. Tumor embolization to the lungs may be one of the important reasons for the poor results of surgery in this disease. Two possible technical and therapeutic modifications are suggested to prevent or neutralize this phenomenon.

Aldosterone-binding globulin-induced hypertension in the rat. A new experimental model

A thermostable urinary homologue of the plasma aldosterone-binding globulin (ABG), designated ABG-TsU, was isolated and purified by differential ultrafiltration, ion exchange chromatography, and gel filtration to electrophoretic homogeneity. Scatchard plot analysis using highly purified ABG-TsU demonstrated reversible high-affinity low-capacity binding at separate sites for aldosterone and dehydroepiandrosterone sulfate (DHEA-SO4). ABG-TsU injected intraperitoneally (i.p.) in male rats resulted in sustained hypertension after 5 to 8 days, characterized after 12 days by no changes in plasma Na+ K+, aldosterone, or plasma renin activity (PRA). No histological changes could be detected in the kidneys, brains, or hearts, nor evidence of adrenocortical hyperplasia. This hypertension appears to be aldosterone-dependent since it is prevented by bilateral adrenalectomy or administration of a spironolactone, but not by adrenalectomy when aldosterone is given concomitantly with ABG-TsU. Hemodynamic characterization of this hypertension was carried out in rats after treatment with ABG-TsU or saline i.p. for 14 days. Cardiac output (CO) was measured using the reference sample microsphere method. ABG-TsU-treated rats had significantly higher mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and CO, while no difference in total peripheral resistance (TPR) was detected. This new animal model of borderline essential hypertension (EH) induced by ABG-TsU, which has a reversible high-affinity binding for aldosterone, results in adrenal-dependent hypertension due at this early phase to an increase in CO without any change in TPR, which remains inappropriately normal.

Experimental essential hypertension in the rat?

1. A human urinary thermostable glycoprotein (ABG-TsU) believed to be a homologue of the plasma aldosterone-binding globulin (ABG) was isolated and purified by differential ultrafiltration, ion-exchange chromatography and gel filtration to electrophoretic homogeneity; it showed a charge heterogeneity in electrofocussing. 2. ABG-TsU was administered intraperitoneally to male rats in small daily doses (7 microgram/day per rat). Sustained hypertension developed in 5--8 days. 3. The treated rats showed no changes in plasma electrolytes, aldosterone or plasma renin activity; however, a significant increase in heart weight was observed. 4. This hypertension appears to be adrenal dependent since it is prevented by bilateral adrenalectomy or administration of an aldosterone antagonist, but not by adrenalectomy when aldosterone is given concomitantly with ABG-TsU.

Differences in physicochemical and antigenic properties of chlamydial strains

Antigenic analysis of Chlamydia psittaci, C. trachomatis, and Lymphogranuloma venereum (LGV) revealed basic physicochemical differences among the three chlamydial strains. These were manifested in structural, isoelectric points, absorption spectra, and in the characteristics of the chromophobe-containing proteins. The effective period of sonication for C. psittaci and C. trachomatis is around 60 min during which the linkages most susceptible to external sonication forces were broken, releasing all attainable cellular components. Denaturation studies demonstrated that less than 50% of protein content of C. psittaci was denatured after 1 h of sonication, only 5% in the case of C. trachomatis. The protein and carbohydrate content of the most reactive fractions in macrophage-spreading inhibition test were different for LGV and C. trachomatis. The structural differences appear to determine the antigenic properties observed among the chlamydial strains as well as the specificity and probably the mechanisms (s) of cellular immune reactivity to Chlamydiae. This in turn may explain the failure of chlamydial vaccines, prepared from stock strains, to protect immunized children against 'wild' chlamydial strains.

Esophageal reconstruction: an experimental approach to the control of reflux after esophageal resection

A study of the properties of replacement gastric tubes and colonic segments, and their use in the prevention of reflux after esophageal resection indicates that, in order to prevent reflux, these tubes must be maintained in a subdiaphragmatic position. Gastric tubes have a higher intrinsic pressure barrier than colonic tubes--a 2.5- to 6-cm segment prevents reflux and the tube maintains a pressure barrier 10 cm H2O higher than stomach presure, whereas colonic segments require 12 cm of subdiaphragmatic length to control reflux and maintain a pressure barrier only 2 cm H2O above gastric pressure. Removal of the intrinsic pressure barrier by myotomy allows free reflux in tubes that previously had prevented reflux.

Bile aspiration: an experimental study in rabbits

It has been shown that bile injected intratracheally in rabbits produces severe pulmonary edema, atelectasis, and focal hemorrhages. The authors investigated the effect of a number of solutions, including physiological concentration of bile, hydrochloric acid pH 1.0, bile salt diluted to 1%, and bile at 100% concentrations. Whenever the bile concentration exceeded 3%, none of the test animals survived. It is not possible to apply directly the results of an experimental animal study to humans. However, the severity of the pulmonary changes produced force the conclusion that bile is a potentially dangerous aspirate in humans.