Optical model for light distribution during transscleral cyclophotocoagulation

Transscleral cyclophotocoagulation (TSCPC) is currently performed clinically as an effective treatment for end-stage glaucoma. We develop a theoretical model for the analysis of optical attenuation phenomena during TSCPC as a basis for selection of an optimal wavelength. A multilayered Monte Carlo model was developed to calculate the fluence and the rate of heat generation in each tissue layer for the wavelengths of Nd:YAG, diode, ruby, krypton yellow, and argon lasers. Of the five wavelengths under study, our theoretical results suggest that the diode laser wavelength offers the best penetration through the conjunctiva, sclera, and ciliary muscle and highest absorption within the ciliary pigment epithelium.

TNF is a potent anti-inflammatory cytokine in autoimmune-mediated demyelination

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by localized areas of demyelination. Although the etiology and pathogenesis of MS remain largely unknown, it is generally assumed that immune responses to myelin antigens contribute to the disease process. The exact sequence of events, as well as the molecular mediators that lead to myelin destruction, is yet to be defined. As a potent mediator of inflammation, the cytopathic cytokine, tumor necrosis factor (TNF) has been considered to be a strong candidate in the pathogenesis of MS and its animal model, experimental autoimmune encephalomyelitis (EAE). However, its role in immune-mediated demyelination remains to be elucidated. To determine the contribution of TNF to the pathogenesis of the MS-like disease provoked by the myelin oligodendrocyte glycoprotein (MOG), we have tested mice with an homologous disruption of the gene encoding TNF. Here we report that upon immunization with MOG, mice lacking TNF develop severe neurological impairment with high mortality and extensive inflammation and demyelination. We show further that inactivation of the TNF gene converts MOG-resistant mice to a state of high susceptibility. Furthermore, treatment with TNF dramatically reduces disease severity in both TNF-/- mice and in other TNF+/+ mice highly susceptible to the MOG-induced disease. These findings indicate that TNF is not essential for the induction and expression of inflammatory and demyelinating lesions, and that it may limit the extent and duration of severe CNS pathology.

Lymphoma presenting as an intramuscular mass

BACKGROUND

Resection of an intramuscular mass without tissue diagnosis can lead to unnecessary surgery.

METHOD

During a 4.5-year period 19 previously healthy patients referred with an undiagnosed soft tissue tumour were found to have intramuscular non-Hodgkin's lymphoma. In seven patients this was the only focus of disease (Stage IE). Patients were treated with chemotherapy or radiotherapy alone or in combination.

RESULTS

After mean follow-up of 43 months all of the patients with stage IE lymphoma are alive and disease free.

CONCLUSION

Primary intramuscular non-Hodgkin's lymphoma has a good prognosis. The importance of a tissue diagnosis by needle core biopsy is emphasized.

Medical causes on stillbirth certificates in England and Wales: distribution and results of hierarchical classifications tested by the Office for National Statistics

OBJECTIVE

To produce a classification of stillbirths registered in England and Wales compatible with a previously described classification for neonatal deaths; to compare national data for intrapartum stillbirths with those for the remaining stillbirths; and to report on stillbirths with a gestational age of 24 to 27 completed weeks first made registrable on 1 October 1992.

DESIGN

Algorithms were developed and tested to derive hierarchical cause classifications making use of multiple causes mentioned on stillbirth certificates.

RESULTS

The additional information available since 1986 on cause and time of death of stillbirths, classified in a hierarchical fashion allows a more meaningful interpretation of the available information on the causes of stillbirth than was previously possible and does not perturb ongoing trends. Antepartum deaths without a classifiable cause contributed the majority: between 1992 and 1994 they accounted for 43% if mentions of asphyxial conditions are regarded as classifiable causes, and 82% if not considered as causal. Stillbirths described as occurring intrapartum are consistently of higher gestational age and birthweight than the remainder, lending validity to the time of death given.

CONCLUSIONS

The national use of a classification including reported time of death of the fetus and mentions of asphyxial conditions is justifiable, providing a distinction is made between associated mentions and causal conditions. Better and more complete clinical information on stillbirth certificates will contribute further to understanding of their causes.

Characterization of tumor necrosis factor-deficient mice

Although tumor necrosis factor (TNF) initially came to prominence because of its anti-tumor activity, most attention is now focused on its proinflammatory actions. TNF appears to play a critical role in both early and late events involved in inflammation, from localizing the noxious agent and amplifying the cellular and mediator responses at the local site and systemically, to editing (e.g., apoptosis) injured cells or effete immune cells and repairing inflammatory damage. We have generated mice deficient in TNF (TNF-/- mice) and have begun to examine the multiple functions attributed to TNF. TNF-/- mice develop normally and have no gross structural or morphological abnormalities. As predicted, they are highly susceptible to challenge with an infectious agent (Candida albicans), are resistant to the lethality of minute doses of lipopolysaccharide (LPS) following D-galactosamine treatment, have a deficiency in granuloma development, and do not form germinal centers after immunization. Phagocytic activity of macrophages appears relatively normal, as do T cell functions, as measured by proliferation, cytokine release, and cytotoxicity. B cell response to thymus-independent antigens is normal, but the Ig response to thymus-dependent antigen is reduced. Surprisingly, cytokine production induced by LPS appears essentially intact, with the exception of reduced colony-stimulating factor activity. Other unexpected findings coming from our initial analysis are as follows. (i) TNF has low toxicity in TNF-/- mice. (ii) TNF-/- mice show an anomalous late response to heat-killed Corynebacterium parvum. In contrast to the prompt response (granuloma formation, hepatosplenomegaly) and subsequent resolution phase in C. parvum-injected TNF+/+ mice, similarly treated TNF-/- mice show little or no initial response, but then develop a vigorous, disorganized inflammatory response leading to death. These results suggest that TNF has an essential homeostatic role in limiting the extent and duration of an inflammatory process-i.e., an anti-inflammatory function. (iii) In contrast to the expectation that TNF+/+ mice and TNF+/- mice would have identical phenotypes, TNF+/- mice showed increased susceptibility to high-dose LPS lethality, increased susceptibility to Candida challenge, and delayed resolution of the C. parvum-induced inflammatory process, indicating a strong gene dose requirement for different actions of TNF.

Compound heterozygosity for the shared epitope and the risk and severity of rheumatoid arthritis in extended pedigrees

The objective was to explore the role of HLA-DRB1 genes in determining disease severity in rheumatoid arthritis (RA). The population comprised extended pedigrees of 17 multicase RA families. Family members were genotyped for both HLA-DRB1 alleles using restriction fragment length polymorphism (RFLP). Identification of HLA-DRB1*04 variants was performed using the Multiplex ARMS-RFLP technique. Compound heterozygote individuals carrying two different alleles containing the shared epitope (SE) were at greatest risk of developing RA (odds ratio = 36, 95% CI 9.1-143). A synergistic or additive effect of these alleles is suggested. Individuals carrying no SE alleles expressed milder disease, as measured by the Spread Severity (SS) index, compared to compound heterozygotes (P = 0.045). Compound heterozygosity was not invariably associated with severe disease with six (50%) having clinically mild disease at a median age of 57.5 yr and median disease duration of 16 yr. Inheriting two different SE-bearing alleles results in an increased risk of RA and, on average, greater disease severity. This is not, however, invariably associated with severe disease, making it of limited use as a predictor of prognosis.

Dendritic cell development in culture from thymic precursor cells in the absence of granulocyte/macrophage colony-stimulating factor

The earliest lymphoid precursor population in the adult mouse thymus had previously been shown to produce not only T cells, but also dendritic cell (DC) progeny on transfer to irradiated recipients. In this study, culture of these isolated thymic precursors with a mixture of cytokines induced them to proliferate and to differentiate to DC, but not to T lineage cells. At least 70% of the individual precursors had the capacity to form DC. The resultant DC were as effective as normal thymic DC in the functional test of T cell stimulation in mixed leukocyte cultures. The cultured DC also expressed high levels of class I and class II major histocompatibility complex, together with CD11c, DEC-205, CD80, and CD86, markers characteristic of mature DC in general. However, they did not express CD8 alpha or BP-1, markers characteristic of normal thymic DC. The optimized mixture of five to seven cytokines required for DC development from these thymic precursors did not include granulocyte/macrophage colony stimulating factor (GM-CSF), usually required for DC development in culture. The addition of anti-GM-CSF antibody or the use of precursors from GM-CSF-deficient mice did not prevent DC development. Addition of GM-CSF was without effect on DC yield when interleukin (IL) 3 and IL-7 were present, although some stimulation by GM-CSF was noted in their absence. In contrast, DC development was enhanced by addition of the Flt3/Flk2 ligand, in line with the effects of the administration of this cytokine in vivo. The results indicate that the development of a particular lineage of DC, probably those of lymphoid precursor origin, may be independent of the myeloid hormone GM-CSF.

Recent trends in the incidence of multiple births and associated mortality in England and Wales

AIM

To review trends in multiple births and associated mortality in England and Wales since 1975, in the light of trends for earlier years; to assess, within the limitations of the available data, the extent of any association between multiple birth rates and assisted conception and drugs used for subfertility.

METHODS

Data collected routinely in England and Wales, between 1975 and 1994, were retrospectively reviewed. These comprised Office of Population Censuses and Surveys (OPCS) data collected at the registration of live and stillbirths and deaths occurring under the age of 1 year in England and Wales from 1975 onwards. Department of Health data about NHS prescriptions dispensed outside hospitals within England for drugs which could be used in the medical management of subfertility were also included.

RESULTS

The proportion of pregnancies that resulted in a registered multiple birth increased from a low of 9.9 per thousand in 1975 to 13.6 per thousand in 1994. Up to 1992, the increase was seen in all age groups except for women under 20, with the most substantial increase being in women aged 35 to 39. The rise in the rate of triplet and other higher order births was much steeper than that for all multiple births, increasing from 0.13 sets of triplets per thousand maternities in 1975, to 0.41 in 1994. Prescriptions dispensed for selected drugs that may be used for the medical management of subfertility and assisted conception became more common over this period. The fragmented nature of the data precluded direct comparison with changes in multiple birth rates, however.

CONCLUSIONS

Although the causes of the rise since 1980 in multiple birth rates in general, and the dramatic rise in the triplet rate in particular, cannot be ascertained or quantified directly from routinely collected data, drugs used for subfertility and more recently, assisted conception, probably had a major role.

An adolescent hepatitis B immunisation program. The Preston experience

An adolescent hepatitis B immunisation program was conducted in all post primary schools in the City of Preston, Melbourne, Victoria, in 1993. The program was funded entirely by the City of Preston using SmithKline Beecham, Engerix B Adult Vaccine. A total of 857 Year 9 students in 8 schools were offered a three-dose course of Hepatitis B vaccine; 85% of all students elected to enter the program; 78% of all students completed the program; 95% of students who started the program completed the three-dose schedule. No side effects from the 2041 doses were reported. The program was well accepted and tolerated by the students with minimum side effects at a total cost of $34 per completed course.