The molecular diversity of the methanogenic community in a hypereutrophic freshwater lake determined by PCR-RFLP

AIMS

To combine database-held sequence information with a programme of experimental molecular ecology to define the methanogenic community of a hypereutrophic lake by a PCR-restriction fragment length polymorphism (RFLP) analysis.

METHODS AND RESULTS

Methanogen diversity in a hypereutrophic freshwater lake was analysed using 16S rDNA PCR-RFLP. Database-held 16S rRNA gene sequences for 76 diverse methanogens were analysed for specific restriction sites that permitted unequivocal differentiation of methanogens. Restriction digestion and agarose gel electrophoresis of the 16S rDNA from selected methanogen pure cultures generated observed restriction profiles that corroborated the expected patterns. This method was then tested by analysing methanogen diversity in samples obtained over 1 year from sediment and water samples taken from the same sampling site.

CONCLUSIONS

Restriction analysis of the 16S rRNA gene sequences from 157 methanogen clones generated from lakewater and sediment samples showed that over 50% were similar to Methanoculleus spp. Furthermore, a total of 16 RFLP types (1-16) were identified, eight of which contained no cultured representative archaeal 16S rRNA gene sequences.

SIGNIFICANCE AND IMPACT OF THE STUDY

This RFLP strategy provides a robust and reliable means to rapidly identify methanogens in the environment.

Solution rheology of kappa-carrageenan in the ordered and disordered conformations

The order-disorder conformational transition of kappa-carrageenan, induced by both electrolyte and temperature, was found to give rise to significantly different rheological properties under shear flow, extensional flow, and small deformation oscillation regimes. Shear flow displayed only shear thinning or Newtonian behavior, depending of the chain conformation. A larger range of properties was observed in elongational flow. Strain-thinning behavior was observed in the ordered conformation while strain thickening occurred in the disordered conformation. These results are discussed as a function of the chain conformation.

A rheological study of the order-disorder conformational transition of xanthan gum

The rheological properties of a moderately concentrated solution of xanthan gum in both the ordered and the disordered state have been studied. Oscillatory shear, steady shear flow, and extensional flow experiments have been performed at different temperatures, covering the order-disorder transition determined by differential scanning calorimetry (DSC). The principle of time/temperature superposition was applied to the xanthan solutions for the different types of flow. Although a master curve covering six decades of frequency could be obtained for the storage modulus over the entire investigated temperature range, less agreement was found for the other modulus. This indicates that the order-disorder transition reflects changes on the molecular scale and slight modification of the physical network structure. To the authors' knowledge, this is the first time that this transition has been observed using these different rheological techniques.

Are we meeting the psychological needs of Black African HIV-positive individuals in London? Controlled study of referrals to a psychological medicine unit

The changing pattern of HIV infection in the UK includes an increase in the number of infections acquired as a result of heterosexual contact and Black African individuals represent a sizeable proportion of those affected. In most UK centres for the treatment of HIV infection, clinicians have limited experience in caring for Black African patients, and there is a dearth of information about the recognition and management of mental health problems in this patient group. In this investigation the proportion of Black African individuals looked after in a large centre for the care of HIV infection in London was compared with the proportion of such patients referred for specialist mental health help, the results revealing that Black Africans were almost three times less likely to be referred for specialist mental health care. A case control investigation of those referred to mental health services showed that Black Africans were more likely to be suffering from AIDS at the time of referral, be referred for assessment of possible organic brain disease, and more likely to be found to be suffering from major depression or organic brain disease. Reasons for the lesser likelihood of referral to the mental health service are considered, including the possible failure of staff to recognize psychological morbidity in Black Africans, or reluctance and fear on the part of patients to be referred to services that may be perceived as threatening.

The effect of hydroxyl radicals on the rheological performance of hylan and hyaluronan

Shear flow, dynamic oscillation and extensional viscosity measurements were used to compare the rheological performance of several hylan samples (M(v) 1.6, 3.2, 3.7, 4.7 and 5.6x10(6)) and hyaluronan (M(v) 1.4 and 1.8x10(6)) before and after hydroxyl radicals (*OH) induced degradation. It was found that the higher molecular weight cross-linked structure of hylan was more resistant to degradation than hyaluronan and that this superior stability was reflected in various rheological parameters. The *OH degradation of the initial hylan and hyaluronan samples produced a range of polysaccharides based on hylan and hyaluronan with molecular weight covering a range from 0.5-5.6x10(6). The rheological parameters associated with the polysaccharides could then also be studied. Zero shear values of the complex viscosity (eta*), dynamic viscosity (eta') and shear viscosity (eta) were calculated using the method of Morris(1) and shown to approach the same value at zero shear or frequency. An adaptation of the method of Gibbs et al. gave a 'master curve' for the storage and loss modulus of hyaluronan and hylan, which encompasses a 10-fold molecular weight and a 5-fold concentration variation. In all instances for hylan, the storage modulus predominates over the loss modulus, whereas for hyaluronan, the reverse is true, demonstrating the greater elasticity of hylan throughout the whole experimental range of molecular weights and concentrations.

The changing pattern of mental health problems in HIV infection: the view from London, UK

As we end the second decade with AIDS, profound changes in our understanding of its aetiology, mechanism of disease and its treatment have led to significant improvements in survival, disease progression and quality of life for those individuals with HIV infection who are fortunate enough to have access to health care and to treatments for the infection and its complications. Unsurprisingly, the psychological and social consequences of HIV have also seen important shifts, giving rise to new and unforeseen difficulties, as well as a greater sense of hope. Here, some of the changes seen among people with HIV infection being looked after in a Central London teaching hospital and referred to the mental health services are reviewed and discussed.

Sexual dysfunction in gay and bisexual men with HIV infection: evaluation, treatment and implications

Sexual dysfunction problems are common in people with HIV infection, but their relevance has been recently highlighted in response to the increased survival shown by many individuals with HIV, and the publicity surrounding the development of new treatments for male sexual dysfunction. Thirty-four gay/bisexual men with HIV infection presenting with sexual dysfunction were assessed. Antiretroviral combination therapy including protease inhibitors was taken by 44%, other combinations not including protease inhibitors by 24%, while 32% were not taking any antiretrovirals. Primarily psychogenic sexual dysfunction was thought to be present in 44%, primarily organic dysfunction in 22% and a mixed aetiology in 34%. Treatments offered included psychological interventions and physical methods of treatment, alone or in combination. Treatment was effective, with 76% reporting resolution of the problems, 14% reporting improvement and only 10% reporting no change. Practical and ethical issues raised by the findings are discussed.

Asymptomatic Chiari Type I malformations identified on magnetic resonance imaging

OBJECT

Chiari Type I malformation (CMI) is a congenital disorder recognized by caudal displacement of the cerebellar tonsils through the foramen magnum and into the cervical canal. Frequently, associated findings include abnormalities of nearby bony and neural elements as well as syringomyelia. Cerebellar tonsillar ectopia is generally considered pathological when greater than 5 mm below the foramen magnum. However, asymptomatic tonsillar ectopia is an increasingly recognized phenomenon, the significance of which is poorly understood.

METHODS

The authors retrospectively reviewed the records of all brain magnetic resonance (MR) images obtained at our hospital over a 43-month period in an attempt to ascertain the relative prevalence and MR imaging characteristics of asymptomatic CMIs. Of 22,591 patients who underwent MR imaging of the head and cervical spine, 175 were found to have CMIs with tonsillar herniation extending more than 5 mm below the foramen magnum. Of these, 25 (14%) were found to be clinically asymptomatic. The average extent of ectopia in this population was 11.4 +/- 4.86 mm, and was significantly associated with a smaller cisterna magna. Syringomyelia and osseous anomalies were found in only one asymptomatic patient.

CONCLUSIONS

The authors suggest that the isolated finding of tonsillar herniation is of limited prognostic utility and must be considered in the context of all available clinical and radiographic data. Strategies for treating patients with asymptomatic CMIs are discussed.

BUBR1 phosphorylation is regulated during mitotic checkpoint activation

Eukaryotic cells have evolved a mechanism that delays the progression of mitosis until condensed chromosomes are properly positioned on the mitotic spindle. To understand the molecular basis of such monitoring mechanism in human cells, we have been studying genes that regulate the mitotic checkpoint. Our early studies have led to the cloning of a full-length cDNA encoding MAD3-like protein (also termed BUBR1/MAD3/SSK1). Dot blot analyses show that BUBR1 mRNA is expressed in tissues with a high mitotic index but not in differentiated tissues. Western blot analyses show that in asynchronous cells, BUBR1 protein primarily exhibits a molecular mass of 120 kDa, and its expression is detected in most cell lines examined. In addition, BUBR1 is present during various stages of the cell cycle. As cells enter later S and G2, BUBR1 levels are increased significantly. Nocodazole-arrested mitotic cells obtained by mechanical shake-off contain BUBR1 antigen with a slower mobility on denaturing SDS gels. Phosphatase treatment restores the slowly migrating band to the interphase state, indicating that the slow mobility of the BUBR1 antigen is attributable to phosphorylation. Furthermore, purified recombinant His6-BUBR1 is capable of autophosphorylation. Our studies indicate that BUBR1 phosphorylation status is regulated during spindle disruption. Considering its strong homology to BUB1 protein kinase, BUBR1 may also play an important role in mitotic checkpoint control by phosphorylation of a critical cellular component(s) of the mitotic checkpoint pathway.

The physical association and phosphorylation of Cdc25C protein phosphatase by Prk

prk encodes a protein serine/threonine kinase involved in regulating M phase functions during the cell cycle. We have expressed His6-Prk and His6-Cdc25C proteins using the baculoviral vector expression system. Purified recombinant His6-Prk, but not a kinase-defective mutant His6-PrkK52R, is capable of strongly phosphorylating His6-Cdc25C in vitro. Co-immunoprecipitation and affinity column chromatography experiments demonstrate that GST-Prk and native Cdc25C interact. When co-infected with His6-Prk and His6-Cdc25C recombinant baculoviruses, sf-9 cells produce His6-Cdc25C antigen with an additional slower mobility band on denaturing polyacrylamide gels compared with cells infected with His6-Cdc25C baculovirus alone. In addition, His6-Cdc25C immunoprecipitated from sf-9 cells co-infected with His6-Prk and His6-Cdc25C baculoviruses, but not with His6-PrkK52R and His6-Cdc25C baculoviruses, contains a greatly enhanced kinase activity that phosphorylates His6-Cdc25C in vitro. Moreover, phosphopeptide mapping shows that His6-Prk phosphorylates His6-Cdc25C at two sites in vitro and that the major phosphorylation site co-migrates with the one that is phosphorylated in vivo in asynchonized cells. Further studies reveal that His6-Prk phosphorylates Cdc25C on serine216, a residue also phosphorylated by Chk1 and Chk2. Together, these observations strongly suggest that Prk's role in mitosis is at least partly mediated through direct regulation of Cdc25C.

The burden of care: the impact of HIV-associated dementia on caregivers

It has been suggested that up to 15% of patients with AIDS may develop HIV-associated dementia. The syndrome may be either abrupt or insidious and is characterized by poor prognosis. Increasing cognitive impairment will necessitate the patient receiving a substantial amount of care and support in the community in addition to medical treatment and periods of hospitalization. The impact of caregiver burden is reasonably well documented in Alzheimer's disease, but there is a dearth of literature relating to caregiving and HIV-associated dementia. The current investigation is an observational study based on a small group of individuals which evaluates the experiences of these particular individuals as they care for their partner, friend, or son with HIV-associated dementia. The caregivers experience the stresses described in the non-HIV dementia literature; however, the nature of HIV disease means that there are issues involved in caring for this patient group that distinguish it from other types of dementia care; these include difficulties relating to specific HIV medical problems and problems with service shortfalls. The caregiver is more likely to be a parent or partner than a child of the patient due to the early age onset seen in this disease compared with Alzheimer's disease. Caregivers express their need for information about dealing with the everyday physical, behavioral, and emotional challenges and about services and benefits available. The interviewees expressed concerns over a perceived lack of communication and information from professionals involved in the patient's care and in the provision of services. The study offers an insight into the relevant issues affecting such caregivers and suggests areas of unmet needs that might be addressed in future service provisions.

Human Bub1: a putative spindle checkpoint kinase closely linked to cell proliferation

Eukaryotic cells have evolved a mechanism that delays the onset of anaphase until chromosomes are properly positioned on the spindle. To understand the molecular basis of such surveillance mechanism in human cells, we have cloned a full-length cDNA encoding a putative mitotic checkpoint kinase termed hBub1. Sequence comparison reveals that hBub1 is a structurally conserved protein, sharing 23% amino acid residue identity with BUB1 of budding yeast. In addition, the NH2-terminal portion (161 amino acids) of hBub1 shows a significant homology to yeast MAD3, a protein also known to be involved in the mitotic checkpoint response pathway. Northern blot analyses show that the hBub1 mRNA level is abundantly expressed in tissues or cells with a high mitotic index. When Dami cells undergo terminal differentiation after treatment with phorbol ester, hBub1 expression in this cell line is down-regulated rapidly. The hBub1 protein level is low in G1 and remains relatively constant in S, G2, and M phases. Immunofluorescence analysis shows that hBub1 protein colocalizes with a centromere-kinetochore antigen CREST in interphase, mitotic prophase, and nocodazole-treated cells. Antibody electroporation experiments show that hBub1 is an important component of the spindle checkpoint pathway. Furthermore, fluorescence in situ hybridization analysis maps the hBub1 gene to chromosome 2q12-13. Our studies suggest that hBub1 expression is restricted to proliferating cells and appears to be involved in regulating cell cycle progression. The molecular cloning of hBub1 cDNA will facilitate the study of its role in spindle checkpoint control as well as its potential role in certain genetic disorders.

Mental health problems in older adults with HIV referred to a psychological medicine unit

Although HIV is still seen by many as a disease affecting younger adults, it is known that at least 11% of individuals with AIDS in Britain are over the age of 50. It is likely that this older age representation will continue and increase and whilst much is known about the psychological wellbeing of younger individuals with HIV, it is crucial that we consider the differing experiences and needs of older adults with the disease. Fifty-two adults with HIV over the age of 54 were referred to the Department of Psychological Medicine between June 1990 and December 1996. Data for these patients were compared with corresponding information for a random sample of younger patients with HIV. The older adults were found to differ significantly from the younger individuals on a variety of social, psychological and medical variables including social isolation, employment worries, sexuality, previous psychiatric history and stage of HIV at referral. It seems that current HIV services may actually alienate a significant proportion of potential users through not being sensitive to the needs and views of these older individuals. This must be addressed by policy makers and practitioners to ensure that psychiatric and psychological services become more acceptable and accessible to the older adult.

Are reported stress and coping style associated with frequent recurrence of genital herpes?

OBJECTIVES

This paper reports on the cross sectional data from the longitudinal study examining the impact of genital herpes simplex virus (HSV) infection on quality of life. In particular the report sought to study the relation between recurrence of genital HSV and coping style, mood, personality, and quality of life, among other factors.

SETTING AND SUBJECTS

116 patients with a known history of genital herpes simplex infection attending the Department of Genitourinary Medicine at Chelsea and Westminster Hospital.

METHODS

Psychosocial factors (stress, anxiety, depression, health locus of control, personality, social support, coping skills, and quality of life) and the reported frequency of genital herpes episodes were measured using self administered questionnaires designed to examine the relation between psychosocial status and the frequency of genital HSV episodes.

RESULTS

The number of recurrences reported by patients was significantly related to the style of coping skills used. Higher recurrences were less likely to use problem focused coping skills of planning and active coping, and the emotion focused coping skills of positive reinterpretation and growth. There was a significant difference in the number of patients who believed that psychological stress was related to the number of recurrences they experienced. This belief was related to neuroticism on the Eysenck Personality Questionnaire scale, and not to any of the other measures investigated.

CONCLUSION

The findings suggest that it is the way individuals cope, and their personality characteristics rather than actual levels of psychological stress, that influence their belief in a link between recurrent genital HSV and stress. HSV may become the focus of existing concerns and be viewed as the physical manifestation of stress.

Regional specialization in the eye of the sphingid moth Manduca sexta: blue sensitivity of the ventral retina

The compound eye of the tobacco hornworm moth Manduca sexta contains green-, blue-, and ultraviolet-sensitive photoreceptors. Electroretinogram spectral-sensitivity measurements were recorded from different regions of the retina in order to broadly map the distribution of the three receptor types. The relative contribution of the three receptors to spectral-sensitivity curves was estimated by fitting theoretical curves based on the absorption spectra of the three rhodopsins. This analysis indicated that the dorsal retina is green and ultraviolet dichromatic, with green-sensitive cells greatly predominating. The ventral retina is trichromatic with a substantial population of blue- and ultraviolet-sensitive receptors. We previously showed that flower visitation for nectar feeding is mediated mainly by blue-sensitive cells. Their localization in the ventral retina seems an appropriate adaptation of the receptor mosaic, since the moths hover above flowers as they feed.