Opening up on airways: the purported effect of nasorespiratory obstruction on dentofacial growth

Nasorespiratory obstruction has been purported to influence dentofacial growth adversely. This has sparked considerable debate for decades with a resurgence in interest in 'airway friendly orthodontics' among both general and specialist dental practitioners. This critical review aims to evaluate the current literature relating to two questions: does nasorespiratory obstruction alter dentofacial growth, and does early intervention targeted at alleviating nasorespiratory obstruction improve dentofacial growth? The strength of association between nasorespiratory obstruction, mouth breathing and a long face is weak. The common methodological flaws in research include unblinded and cross-sectional study designs, a lack of adequate controls, inadequate follow-up, subjective assessments and inadequate statistical power. Vertical dentofacial growth has a strong genetic influence, which implies a relatively minor contribution of environmental factors including airway obstruction. The current evidence does not support recommending procedures, such as adenotonsillectomy and maxillary expansion, with the singular aim of negating a hyperdivergent (vertical) dentofacial growth pattern. In light of low-quality evidence, both the World Health Organization guidelines and ethical principles dictate that greater emphasis is placed on avoiding harm and wastage of resources over alternative options. These findings call for quality improvement in undergraduate and postgraduate curricula and continuing professional development for health professionals.

Prevalence and genotype distribution of TT virus in various specimen types from thalassaemic patients

Peripheral blood mononuclear cells (PBMC), plasma, saliva and urine samples were collected from 50 thalassaemic patients for TT virus (TTV) detection by two sets of PCR. The set B nested PCR was more sensitive than the widely used NG hemi-nested PCR with TTV positive rates approximately PBMC: 98% vs. 70%; plasma: 92% vs. 66%; saliva: 62% vs. 22%; urine: 22% vs. 6%. All 50 patients had TTV detected in one or more specimens, with 16% of patients being positive in all four specimen types: 40% positive in PBMC, plasma and saliva; 30% positive in PBMC and plasma. In 82 NG hemi-nested PCR-positive samples TTV genotype was identified, 68.3% had a single genotype, 25.6% had multiple genotypes and 6.1% were uncharacterized. The positive rates for genotypes by specimen were: G1 (36/82), G2 (49/82), G3 (2/82), G4 (7/82), G5 (1/82) and G6 (3/82). Among the 42 patients for whom the genotype was examined, 42.9% had single-type infection, 45.2% had co-infections and 11.9% had uncharacterized genotypes. Sixteen of them had TTV detected both in PBMC and plasma with seven having identical genotypes in both samples. Eight patients had TTV detected in PBMC, plasma and saliva; two of them harboured identical genotypes in all three samples. The results indicate that, apart from hepatocytes, PBMC is a major cell type for TTV infection occurs. Shedding of TTV in urine and saliva is common and may have a significant role in nonblood-borne transmission among the general population. TTV-infected patients often harbour multiple genotypes suggesting infection with one genotype does not necessarily confer protection against the others. No correlation between TTV infection and liver dysfunction was observed.

High carriage rate of TT virus in the cervices of pregnant women

Prevalence studies of the recently identified TT virus (TTV) have suggested that parenteral transmission is a common route of infection, but other routes also appear likely. In this study, a high rate of cervical carriage (66%) of TTV DNA was found by polymerase chain reaction, which suggests that perinatal and sexual transmission is possible.

Evaluation of extraction methods from paraffin wax embedded tissues for PCR amplification of human and viral DNA

AIM

To evaluate the efficiency of phenol/chloroform, microwave, and Qiagen spin column based DNA extractions from paraffin wax embedded tissue for use in the polymerase chain reaction (PCR). In addition, to assess the reliability of amplifying a housekeeping gene to indicate successful viral DNA extraction.

METHODS

DNA samples extracted from 20 blocks of cervical carcinoma tissues using the three methods were subjected to PCRs targeting 509 bp and 355 bp of the beta globin gene, and 450 bp and 150 bp of human papillomavirus (HPV) DNA.

RESULTS

Microwave extraction showed the highest positive rate for beta globin PCR, whereas the spin column method was the most efficient for HPV DNA extraction. When the 509 bp beta globin and 450 bp HPV PCR results were correlated, two of 10, eight of 12, and nine of 10 beta globin positive extractions prepared by means of the phenol/chloroform, microwave, and spin column methods, respectively, yielded HPV DNA of the expected size. For the beta globin negative samples, HPV was detected in three of 10, two of eight, and four of 10 samples.

CONCLUSIONS

HPV DNA extraction was most efficient using the Qiagen spin column and had the highest positive predictive value when a housekeeping gene was used as an indicator of successful viral DNA extraction; the phenol/chloroform method was the least efficient. The potential drawbacks of some extraction methods when using a human housekeeping gene to assess the quality of viral DNA extraction need to be considered.

Association of human beta-herpesviruses with the development of cervical cancer: bystanders or cofactors

BACKGROUND/AIM

Human papillomaviruses (HPVs) are important, but not sufficient, for the development of cervical cancer. All three human beta-herpesviruses--cytomegalovirus (CMV) and human herpesviruses (HHV) types 6 and 7--have been detected in the cervix. In addition, CMV and HHV-6 can interact with HPVs in vivo. This study examined the possible role of beta-herpesviruses in cervical cancer development.

METHODS

HPV, CMV, HHV-6, and HHV-7 were detected by the polymerase chain reaction using cervical scrapes taken at colposcopy from 388 women. HPV types were identified using restriction fragment length polymorphisms. Colposcopy guided biopsies were taken from abnormal areas, and the histological findings were regarded as the final diagnoses. The associations between herpesvirus infection and the degree of cervical lesion were analysed with respect to HPV status.

RESULTS

Of the 388 women, 51.8% had a normal cervix, 14.4% had cervical intraepithelial neoplasia grade 1 (CIN1), 8.2% had CIN2, 19.3% had CIN3, and 6.2% had invasive carcinoma. Overall, the positive rates for high, intermediate, and low risk HPVs were 18.8%, 21.4%, and 5.2%, respectively. Fifteen patients harboured HPVs for which the genotype could not be identified. Positive rates for CMV, HHV-6, and HHV-7 were 9.5%, 3.6%, and 3.4%, respectively. HPV positive patients carried a higher risk for high grade lesions (CIN2/3 or carcinoma) (odds ratio (OR), 5.24; 95% confidence interval (CI), 3.19 to 8.62; chi 2 = 51.79; p < 0.001), whereas those positive for CMV, HHV-6, or HHV-7 did not. Thirteen of 131 patients with high grade lesions had HPV/herpesvirus coinfections, but no association with the cervical lesion was noted. Furthermore, positive rates for herpesviruses among HPV negative, high/intermediate risk HPV negative, and high risk HPV negative subgroups were similarly low and without a significant association.

CONCLUSIONS

The ubiquitous nature of herpesviruses may pose difficulty in elucidating their pathogenic role. These results indicate that CMV, HHV-6, and HHV-7 are bystanders rather than cofactors in the oncogenesis of cervical cancer.

Prevalence and distribution of human herpesvirus 7 in normal brain

Although it has been recognised that human herpesvirus 7 (HHV-7) establishes latent infection in CD4+ T lymphocytes and productive infection in salivary glands, recent data suggest that its in vivo tropism may be more widespread. In this study, the prevalence and distribution of HHV-7 in brain tissues of 30 consecutive post-mortems were examined by nested polymerase chain reaction. For each post-mortem, 10 fresh autopsy tissue samples were collected respectively from the cerebellum, frontal, temporal, parietal, and occipital lobes of both cerebral hemispheres. These patients were aged from 20-95 years (mean = 61.4, SD = 20.2) with a male:female ratio of 2:1. Three patients died of intracranial haemorrhage, the others died of causes unrelated to the central nervous system. Overall, 5% (15/300) of the brain tissue samples were positive for HHV-7 DNA. The positive rates with respect to anatomical positions were similar (0-3/30). When analysed by patient, 36.7% (11/30) were HHV-7 DNA positive. The viral DNA-positive and -negative groups did not show a significant difference in gender or age distribution. The majority (81.8%) of viral DNA-positive patients had HHV-7 DNA detected at only one anatomical position; only two patients had viral DNA detected simultaneously at three anatomical sites. These results suggest that HHV-7 persists in brain tissues of a substantial proportion of the adult population, and in most individuals, its distribution is probably confined to one site rather than pervasive. Further studies to elucidate the role of this ubiquitous virus in neuropathology are warranted.

Survey for the presence and distribution of human herpesvirus 8 in healthy brain

Brain tissues from both sides of the cerebellum and frontal, temporal, parietal, and occipital lobes were collected postmortem from 30 patients for human herpesvirus 8 (HHV-8) detection by PCR. Overall, 42 of 300 (14.0%) samples were positive, with similar rates for each position. Nineteen patients (63.3%) were positive and showed a significant increase in positivity with age (P = 0.007). The results indicate a neuroinvasive and neuropersistent potential of HHV-8.

Presence of human herpesviruses 6, 7, and 8 DNA sequences in normal brain tissue

The three novel human herpesviruses (HHV) 6, 7, and 8 are predominantly, but not exclusively, lymphotropic. In an attempt to elucidate their neurotropism in vivo, viral DNA sequences present in fresh autopsy cortical brain tissues obtained from 84 consecutive Chinese subjects (mean age, 66.9 years; range, 21-98 years) were detected by a nested polymerase chain reaction. These patients were apparently immunocompetent and free of clinical signs of viral diseases. HHV-6 DNA was detected in 36 of 84 (42.9%) patients, and the DNA-positive and -negative groups did not show a significant difference in age or sex distribution. Of the 36 HHV-6 DNA-positive cases, 9 (25%) were variant A and 27 (75%) were variant B. In view of the lower prevalence of variant A than variant B in the adult population, the two variants may share a comparable neuroinvasive potential. HHV-7 and HHV-8 DNA were detected respectively in three and two patients. The low positive rates of HHV-7 and HHV-8 may represent a relatively lower neuroinvasive potential of the viruses. Alternatively, the localization of HHV-7 and HHV-8 may be more restricted and the sampled cortical tissues may not represent the most abundant site of persistence in the nervous system. The results provide molecular evidence of the presence of the three newly identified herpesviruses in brain tissue. The pathogenic role for HHV-7 and HHV-8, as with HHV-6, in neurological diseases should not be overlooked.

High prevalence of human papillomavirus type 58 in Chinese women with cervical cancer and precancerous lesions

The prevalence of human papillomavirus (HPV) among 332 Hong Kong Chinese women with abnormal Papanicolaou smears were determined by polymerase chain reaction and restriction fragment length polymorphism analysis. The overall HPV positive rate was 44.3% with 18.6% (16/86) for normal/inflamed cervices, 36.4% (32/88) for condyloma, 64.7% (33/51) for cervical intraepithelial neoplasia grade 1 (CIN 1), 37.9% (11/29) for CIN 2, 68.3 (41/60) for CIN 3, and 77.8% (14/18) for carcinoma. Double HPV infection was detected in 17 of the 147 positive samples, with a significantly higher proportion in patients with normal or inflamed cervices than those with CIN or carcinoma (31.3% vs 10.5%, P =.029). The six most commonly identified genotypes were HPV 16 (33.3%), HPV 58 (23.8%), HPV 11, 18, 31 (8.8% each), and HPV 33 (6.8%). The worldwide uncommon genotype HPV 58 was found to be the second most common genotype detected in patients with cervical carcinoma (6 of 18 patients). HPV 58 infection showed a significant association with CIN/carcinoma (odds ratio [OR] = 3.98; 95% confidence interval [CI] = 1.22-14.35) and a significant trend of increase in prevalence with increasing severity of cervical lesion (chi(2) = 5.84; P =.016). Among Hong Kong Chinese women with abnormal cervical cytology, the detection of HPV 58 carried a positive predictive value of 68.6% for a cervical lesion of CIN 1 or higher severity. The high prevalence of HPV 58 among Chinese women, particularly in patients with carcinoma, has an implication on the design of HPV detection methods and the development of vaccines.

Doppler shift anisotropy in small angle neutron scattering

The two-dimensional patterns in our small angle neutron scattering (SANS) experiments from rapidly moving aerosols are anisotropic. To test the kinematic theory of two-body scattering that describes the anisotropy, we conducted SANS experiments using a constant source of D2O aerosol with droplets moving at approximately 440 m/s, and varied the neutron velocity from 267 to 800 m/s. The theoretically predicted anisotropy of the laboratory scattering intensities agrees well with the experimental results. Based on an analysis of the scattering intensity in the Guinier region, we also determined the particle velocity. The results are in very good agreement with independent velocity estimates based on supersonic flow measurements.

Temporal beating of nondegenerate azimuthal modes in nonspherical microdroplets: technique for determining the distortion amplitude

Oscillations that are superimposed on the smooth, exponential decay of light from microcavity modes are observed, and they are characteristic of the temporal beating of adjacent, degeneracy-split azimuthal modes in distorted spheres. The perturbation theory result for the frequency splitting of azimuthal modes in distorted spheres is used to determine the distortion amplitude from the temporal oscillations associated with mode beating. The beating period can be used to determine whether the spectrally measured resonance linewidth Deltaomega(l,n) is broadened by closely spaced, degeneracy-split azimuthal modes of slightly nonspherical droplets.

Different temporal behavior for the forward- and backward-circulating radiation within a microdroplet

Spatially resolved nonlinear scattering of a train of picosecond pulses from ethanol microdroplets is investigated. Different time behavior is observed for light with the same and the opposite sense of circulation as the input-coupled light. The forward-circulating light exhibits a smooth, delayed pulse-to-pulse growth, attributed to increased input coupling with time induced by the laser pulses. The backward-circulating light has an irregular time behavior, attributed to near-backward stimulated Brillouin scattering. Increased scattering as a result of CO(2) (compared with He) dissolved gas is demonstrated by an intensity decrease of the spatially precessed radiation on a cavity resonance.