Does hormone replacement therapy prevent cognitive decline in postmenopausal women?

NO. Hormone replacement therapy (HRT) does not prevent cognitive decline in postmenopausal women-and in fact, it may slightly increase risk (strength of recommendation, A; systematic review, meta-analysis of randomized controlled trials [RCTs], and individual RCT).

BASHH 2018 UK national audit of HIV partner notification

HIV partner notification (PN) is a highly effective strategy to identify people living with undiagnosed HIV infection. This national audit of HIV PN is against the 2015 British Association of Sexual Health and HIV (BASHH)/British HIV Association (BHIVA)/Society of Sexual Health Advisers (SHAA)/National AIDS Trust (NAT) HIV PN standards, developed in response to the 2013 BASHH/BHIVA national HIV PN audit. We report significant improvements in the number of contacts tested per index case, likely due, in part, to clearer definitions as well as better ascertainment and reporting. There remains scope for improvement with informing and testing contactable contacts. Recommendations from this audit include further refinement of definitions and development of a national proforma for HIV PN.

HIV and the menopause: A review

Effective antiretroviral therapy has resulted in a close to normal life expectancy for people living with HIV. This has led to a shift in the age distribution of women living with HIV in the UK, with one in three attending for HIV care estimated to be aged 45-56 years in 2014. The lack of experience of many HIV physicians in managing menopause, and the perceived complexity of managing menopause in women living with HIV by general practitioners means that many women are unable to access appropriate care and support. This is aggravated by the relative paucity of data on menopause in women living with HIV and conflicting results in this field, for example with regard to age of onset of menopause and symptomatology experienced. Furthermore, women living with HIV have unique considerations such as potential interactions between antiretroviral therapy and menopause hormone therapy (previously called hormone replacement therapy) and other physiological concerns such as a multifactorial propensity towards decreased bone mineral density and potentially increased cardiovascular risk. On the whole, menopause hormone therapy is probably underutilised in this group of women due to perceived concerns around drug-drug interactions, as well as fears shared with women in the general population about menopause hormone therapy. Menopausal women should be given adequate information on symptomatology, lifestyle modification and treatment options including menopause hormone therapy. Furthermore, a holistic approach which considers the increased burden of poor mental health in this population is essential.

Perceived need of, and interest in, HIV pre-exposure prophylaxis amongst men who have sex with men attending three sexual health clinics in London, UK

HIV pre-exposure prophylaxis (PrEP) has proven efficacy in reducing the risk of HIV infection in men who have sex with men (MSM), but has not yet been commissioned in the UK. The aim of this study was to investigate perceived need and benefit (or experience of) PrEP among HIV-negative MSM attending sexual health clinics. HIV-negative MSM attending three sexual health centres in London, UK were opportunistically invited to complete a questionnaire. Data collected comprised demographic data and sexual and drug use behaviours as well as questions regarding perceptions of risk and need for PrEP. Logistic regression analysis was undertaken to identify variables predicting acceptability of, and intention to use, PrEP. In addition, data were gathered in respondents already taking PrEP. Eight hundred and thirty-nine questionnaires were analysed. The median age of respondents was 35 years (IQR 28-41, range 18-78), 650 (77%) were of white ethnicity and 649 (77%) had a university education. Four hundred and fifty-six (54%) reported at least one episode of condomless anal sex in the preceding three months, 437 (52%) reported recreational drug use in the preceding three months and 311 (37%) had been diagnosed with a sexually transmitted infection within the preceding six months. Four hundred and sixty-three (64%) of 726 strongly agreed with the statement 'I think I would benefit from PrEP'. Multivariate logistic regression analysis demonstrated that having receptive anal intercourse (RAI) without condoms, having an awareness of the risk of unprotected RAI and having belief in the effectiveness of PrEP were independent predictors for someone thinking they would benefit from taking PrEP. Eight percent of respondents (59/724) had already taken or were currently taking PrEP. The results suggest that individuals at risk are likely to perceive themselves as benefiting from PrEP. The majority perceived their risk of acquiring HIV and benefit from PrEP accurately. Overall they appeared to have little concern over the use of PrEP and generally positive attitudes. Further investigation is warranted to understand why those at risk do not perceive benefit from PrEP.

De-myth-tifying the gender digital divide in Latin America: libraries as intermediaries in bridging the gap

For decades, the gender digital divide has been observed as a concept and a construct throughout countries all over the world. It persists with particular belligerence in areas like Latin America, where myths surrounding its existence have perpetuated disparities in men’s and women’s access to and use of the internet and information and communications technologies (ICTs). In this paper, the author reveals that in order for the gender digital divide to be rectified, it must first be ‘de-myth-tified’, and claims about the divide as nonexistent, unimportant, or due to women’s inherent technophobia systematically discredited. It is then argued that, by exposing the true nature of the divide, spaces are created for libraries to take on a new role in Latin America, as advocates for gender equality in technology and information. Possibilities for improving policy, education, and innovation are explored, with a call for further research in the field. Second Place DJIM Best Article Award.

HIV-indicator-condition-driven HIV testing: clinically effective but still rarely implemented

In the UK, outcomes for people living with HIV are excellent. However, a quarter of those living with HIV do not know their status, and almost half are diagnosed late. Strategies to broaden HIV testing are needed. HIV indicator conditions are those thought to be associated with HIV infection because they share risk factors (eg viral hepatitis) or because they arise as a result of early or late immunodeficiency (eg bacterial pneumonia, Kaposi's sarcoma). They comprise all AIDS-defining conditions, but also many non-AIDS-defining conditions spanning the spectrum of medicine. Patients presenting with indicator conditions should routinely be offered an HIV test. This approach is likely to be clinically effective, because knowledge of HIV status is essential in the management of many conditions. It is cost effective if the prevalence of HIV infection is greater than 0.1%. The strategy removes the need for risk assessment, and is acceptable to patients and healthcare practitioners. If broadly implemented, it is likely to be effective at a public health level, and will help to reduce both undiagnosed HIV and late diagnoses of HIV. Here we review the emerging evidence base that supports the value of routine HIV testing in indicator conditions.

Pharmacokinetic and pharmacodynamic drug interactions between antiretrovirals and oral contraceptives

More than 50 % of women living with HIV in low- and middle-income countries are of reproductive age, but there are limitations to the administration of oral contraception for HIV-infected women receiving antiretroviral therapy due to drug-drug interactions caused by metabolism via the cytochrome P450 isoenzymes and glucuronidation. However, with the development of newer antiretrovirals that use alternative metabolic pathways, options for contraception in HIV-positive women are increasing. This paper aims to review the literature on the pharmacokinetics and pharmacodynamics of oral hormonal contraceptives when given with antiretroviral agents, including those currently used in developed countries, older ones that might still be used in salvage regimens, or those used in resource-limited settings, as well as newer drugs. Nucleos(t)ide reverse transcriptase inhibitors (NRTIs), the usual backbone to most combined antiretroviral treatments (cARTs) are characterised by a low potential for drug-drug interactions with oral contraceptives. On the other hand non-NRTIs (NNRTIs) and protease inhibitors (PIs) may interact with oral contraceptives. Of the NNRTIs, efavirenz and nevirapine have been demonstrated to cause drug-drug interactions; however, etravirine and rilpivirine appear safe to use without dose adjustment. PIs boosted with ritonavir are not recommended to be used with oral contraceptives, with the exception of boosted atazanavir which should be used with doses of at least 35 µg of estrogen. Maraviroc, an entry inhibitor, is safe for co-administration with oral contraceptives, as are the integrase inhibitors (INIs) raltegravir and dolutegravir. However, the INI elvitegravir, which is given in combination with cobicistat, requires a dose of estrogen of at least 30 µg. Despite the growing evidence in this field, data are still lacking in terms of large cohort studies, randomised trials and correlations to real clinical outcomes, such as pregnancy rates, in women on antiretrovirals and hormonal contraception.

Temper outbursts in Prader-Willi syndrome: causes, behavioural and emotional sequence and responses by carers

BACKGROUND

Temper outbursts are common in Prader-Willi syndrome but rarely described in detail. This study investigated the phenomenology of temper outbursts in terms of antecedents, sequence of behaviours and emotions and intervention strategies used.

METHOD

A semi-structured interview about temper outbursts was conducted with the main carers of seven children (9.5 to 16.7 years) and seven adults (24.7 to 47.10 years) with Prader-Willi syndrome (10 male, 4 female). Reliability and validity of the interview results was established.

RESULTS

Various setting events increased and reduced the likelihood of temper outbursts. The most common antecedent was a change to routine or expectation. There were marked similarities in the sequence of behaviours and emotions during temper outbursts, with anger rising quickly followed by expressions of remorse and distress at the end of an outburst.

DISCUSSION

The sequence of behaviours and emotions within outbursts was similar to that described in temper tantrums in typical development. Cognitive and emotional processes are likely to be important in the understanding of temper outbursts with implications for early intervention.

Trichomonas vaginalis: an audit of clinical practice and the demography of infected patients at three London genitourinary medicine clinics

This audit aimed to review clinical standards for Trichomonas vaginalis against British Association of Sexual Health and HIV (BASHH) guidelines. Case notes for patients who had a positive microscopy or culture result were reviewed retrospectively. There was a 0.23% positivity rate for T. vaginalis (n = 84 cases); 96% were female with an average age of 33 years, with proportionally more patients seen in the African/Caribbean population, despite the number of cases being comparable between white (n = 36) and African/Caribbean (n = 34) groups. Seventy percent of patients had both microscopy- and culture-positive results for T. vaginalis. Contact tracing occurred in 87% of patients; 56% of these patients confirmed at least one contact had been treated in the last month. Overall, our data demonstrated a lower positivity rate than expected. Wet microscopy and liquid medium cultures were both important in identifying the infection, but more needs to be done to ensure partner notification has been documented and contacts have been treated.

Primary cervical lymphoma: a rare presentation to a genitourinary medicine clinic

Summary

Primary non-Hodgkin's lymphoma of uterine cervix is a rare diagnosis. We present the case of a 47-year-old woman who presented to our genitourinary (GU) medicine service complaining of a malodorous discharge. Speculum examination revealed a necrotic mass on the cervix. She was referred urgently to gynaecology and subsequent histology revealed a diffuse large B-cell lymphoma. She received six cycles of RCHOP chemotherapy and is now in clinical remission. This case highlights the need for GU medicine physicians to remain vigilant with regard to possible gynaecological malignancies in all of our patients, the need for medical backup within GU medicine clinics and for clear pathways of referral to other specialists to exist.

Disordered follicle development in ovaries of prenatally androgenized ewes

Exposure to excess androgens in utero induces irreversible changes in gonadotrophin secretion and results in disrupted reproductive endocrine and ovarian function in adulthood, in a manner reminiscent of the common clinical endocrinopathy of polycystic ovary syndrome (PCOS). We have recently identified an abnormality in early follicle development in PCOS which we suggested might be an androgenic effect. We propose that altered ovarian function in androgenized ewes is due to prenatal androgens not only causing an abnormality of gonadotrophin secretion, but also exerting a direct effect on the early stages of folliculogenesis. Therefore, in this study, we explored the possible differences between small preantral follicles in the ovarian cortex of androgenized female lambs with those of normal lambs. At 8 months of age, small ovarian cortical biopsies (approximately 5 mm3) were obtained at laparotomy from nine female lambs that had been exposed to androgens in utero from embryonic days 30 to 90 of a 147-day pregnancy, and 11 control female lambs. Further, ovarian tissue was obtained at 20 months of age from ten androgenized and nine control animals. Tissue was either fixed immediately for histology or cultured for up to 15 days prior to fixing. The number of follicles in haematoxylin and eosin-stained sections was counted and recorded along with the stage of development. Before culture, the total follicle density (follicles/mm3 tissue) was not statistically significantly different between the two types of ovary at either 8 or 20 months of age. Furthermore, there were no statistically significant differences in the density of follicles at each stage of development. However, there was a lower percentage of primordial follicles, but a higher percentage of primary follicles, in biopsies taken at 8 months from androgenized lambs when compared with controls. At 20 months, the proportions of follicles at the primordial and primary stages were not significantly different between the two groups, but this was mainly attributable to an increase in the proportion of growing follicles in biopsies from control animals. Culture of ovarian cortex from 8-month-old lambs resulted in a progressive increase in the proportion of growing follicles when compared with tissue fixed on the day of surgery. However, there was no difference between androgenized and control tissue in the percentage of growing follicles. The increase in the proportion of growing follicles in the cortex of androgenized animals is reminiscent of similar observations in human polycystic ovaries and suggests that excess exposure to androgen in early life plays a part in the accelerated progression of follicle development from the primordial to the primary stage in polycystic ovaries.

Symbiogenesis in learning classifier systems

Symbiosis is the phenomenon in which organisms of different species live together in close association, resulting in a raised level of fitness for one or more of the organisms. Symbiogenesis is the name given to the process by which symbiotic partners combine and unify, that is, become genetically linked, giving rise to new morphologies and physiologies evolutionarily more advanced than their constituents. The importance of this process in the evolution of complexity is now well established. Learning classifier systems are a machine learning technique that uses both evolutionary computing techniques and reinforcement learning to develop a population of cooperative rules to solve a given task. In this article we examine the use of symbiogenesis within the classifier system rule base to improve their performance. Results show that incorporating simple rule linkage does not give any benefits. The concept of (temporal) encapsulation is then added to the symbiotic rules and shown to improve performance in ambiguous/non-Markov environments.

Prevalence of sexually transmitted infections and associated risk factors among populations of drug abusers

A cross-sectional survey was conducted of sexually transmitted diseases (STDs) and risky behaviors among 407 drug abusers in treatment facilities in 1998. Infections with human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), herpes simplex virus type 2 (HSV-2), and syphilis were detected by testing serum antibody levels; chlamydia and gonorrhea were detected by testing nucleic acid levels in urine. Logistic regression analysis was performed to measure associations. Prevalences of antibodies were as follows: to HSV-2, 44.4%; to HCV, 35.1%; to HBV, 29.5%; to HIV, 2.7%. The prevalence of syphilis was 3.4%; of chlamydia, 3.7%; and of gonorrhea, 1.7%. Of the 407 subjects, approximately 62% had markers for 1 of the STDs. HIV infection was associated with African American race, use of smokable freebase (crack) cocaine, and STD history. HBV infection was associated with age >30 years, injecting drugs, needle sharing, a history of treatment for drug abuse, and African American race. HCV infection was associated with an age >30 years, injecting drugs, and needle sharing, and HSV-2 infection with an age >30 years, female sex, and African American race. Syphilis was associated with a history of STDs. High prevalences of STDs among drug abusers indicate the need for integration of STD screening and treatment into drug treatment programs.

Abnormal hepatic sinusoidal bile acid transport in an Amish kindred is not linked to FIC1 and is improved by ursodiol

BACKGROUND & AIMS

The mechanism for abnormal hepatic bile acid transport was investigated in an 18-month-old Amish boy who presented with pruritus, poor growth, and severe bleeding episodes. Serum bilirubin, gamma-glutamyltranspeptidase, and cholesterol levels were normal, but prothrombin time and partial thromboplastin time were prolonged and bone alkaline phosphatase level was elevated.

METHODS AND RESULTS

Cholic acid plus chenodeoxycholic acid levels measured by capillary gas-chromatography were 32 times higher than control in serum (34.7 vs. 1.1+/-0.4 microg/dL) but were not detected in liver and were reduced in gallbladder bile. Treatment with ursodiol, a more hydrophilic bile acid, improved pruritus, produced 37% weight gain, and after 2 years reduced serum primary bile acid concentrations about 85%, while accounting for 71% of serum and 24% of biliary bile acid conjugates. On ursodiol therapy, hepatic bile acid synthesis was enhanced 2-fold compared with controls, and microscopy revealed chronic hepatitis without cholestasis. Three younger sisters with elevated serum bile acids responded positively to ursodiol. Microsatellite markers for the FIC1 (gene for Byler's disease) region in these 4 children were inconsistent with linkage to FIC1.

CONCLUSIONS

Conjugated cholic acid and chenodeoxycholic acid were synthesized in the liver and secreted into bile but could not reenter the liver from portal blood and accumulated in serum. In contrast, unconjugated ursodiol entered the liver and was conjugated and secreted into bile. Thus, the enterohepatic circulation of all conjugated bile acids was interrupted at the hepatic sinusoidal basolateral membrane. Unconjugated ursodiol bypassed the hepatic uptake block to enlarge the biliary and intestinal bile acid pools. A mutation in FIC1 recognized among the Amish and linkage of the disorder to FIC1 were excluded.

On meme--gene coevolution

In this article we examine the effects of the emergence of a new replicator, memes, on the evolution of a pre-existing replicator, genes. Using a version of the NKCS model we examine the effects of increasing the rate of meme evolution in relation to the rate of gene evolution, for various degrees of interdependence between the two replicators. That is, the effects of memes' (suggested) more rapid rate of evolution in comparison to that of genes is investigated using a tunable model of coevolution. It is found that, for almost any degree of interdependence between the two replicators, as the rate of meme evolution increases, a phase transition-like dynamic occurs under which memes have a significantly detrimental effect on the evolution of genes, quickly resulting in the cessation of effective gene evolution. Conversely, the memes experience a sharp increase in benefit from increasing their rate of evolution. We then examine the effects of enabling genes to reduce the percentage of gene-detrimental evolutionary steps taken by memes. Here a critical region emerges as the comparative rate of meme evolution increases, such that if genes cannot effectively select memes a high percentage of the time, they suffer from meme evolution as if they had almost no selective capability.

On the evolution of multicelluarity and eusociality

In this article versions of the abstract NKC model are used to examine the conditions under which two significant evolutionary phenomena - multicellularity and eusociality - are likely to occur and why. First, comparisons in evolutionary performance are made between simulations of unicellular organisms and very simple multicellular-like organisms, under varying conditions. The results show that such multicellularity without differentiation appears selectively neutral, but that differentiation to soma (nonreproductives) proves beneficial as the amount of epistasis in the fitness landscape increases. This is explained by considering mutations in the generation of daughter cells and their subsequent effect on the propagule's fitness. This is interpreted as a simple example of the Baldwin effect. Second, the correspondences between multicellularity and eusociality are highlighted, particularly that both contain individuals who do not reproduce. The same process is then used to explain the emergence of eusocial colonies.

On the Baldwin effect

In this article the effects of altering the rate and amount of learning on the Baldwin effect are examined. Using a version of the abstract tunable NK model, it is shown that the adaptation process is sensitive to the rate of learning, particularly as the correlation of the underlying fitness landscape varies. Typically a high learning rate proves most beneficial as landscape correlation decreases. It is also shown that the amount of learning can have a significant effect on the adaptation process, where increased amounts of learning prove beneficial under higher learning rates on uncorrelated landscapes.

Kainate binding proteins possess functional ion channel domains

Kainate binding proteins (KBPs) are highly homologous to ionotropic glutamate receptors; however, no ion channel function has been demonstrated for these proteins. To investigate possible reasons for the apparent lack of ion channel function we transplanted the ion channel domains of five KBPs into glutamate receptors GluR 6 and GluR1. In each case we obtained functional chimeric receptors in which glutamatergic agonists were able to open the KBP-derived ion channel with EC50 values identical to those of the subunit contributing the ligand binding domain. Maximal current amplitudes were significantly smaller than those of the parent clones, however. We also show that the KBP ion channels are highly permeable for calcium and have certain pharmacological properties that are distinct from all other glutamate receptor (GluR) subunits. Thus, all five known KBPs, in addition to their well characterized functional ligand binding sites, have functional ion permeation pathways. Our data suggest that the lack of ion channel function in wild-type KBPs results from a failure to translate ligand binding into channel opening. We interpret our findings to indicate the requirement for a modulatory protein or an additional subunit serving to alter the structure of the KBP subunit complex such that signal transduction is enabled from the ligand binding site to the intrinsically functional ion pore.

Identification of a locus for progressive familial intrahepatic cholestasis PFIC2 on chromosome 2q24

Progressive familial intrahepatic cholestasis (PFIC; OMIM 211600) is the second most common familial cholestatic syndrome presenting in infancy. A locus has previously been mapped to chromosome 18q21-22 in the original Byler pedigree. This chromosomal region also harbors the locus for benign recurrent intrahepatic cholestasis (BRIC) a related phenotype. Linkage analysis in six consanguineous PFIC pedigrees from the Middle East has previously excluded linkage to chromosome 18q21-22, indicating the existence of locus heterogeneity within the PFIC phenotype. By use of homozygosity mapping and a genome scan in these pedigrees, a locus designated "PFIC2" has been mapped to chromosome 2q24. A maximum LOD score of 8.5 was obtained in the interval between marker loci D2S306 and D2S124, with all families linked.

Benign recurrent intrahepatic cholestasis (BRIC): evidence of genetic heterogeneity and delimitation of the BRIC locus to a 7-cM interval between D18S69 and D18S64

Benign recurrent intrahepatic cholestasis (BRIC) is an autosomal recessive liver disease characterized by multiple episodes of cholestasis without progression to chronic liver disease. The gene was previously assigned to chromosome 18q21, using a shared segment analysis in three families from the Netherlands. In the present study we report the linkage analysis of an expanded sample of 14 BRIC families, using 15 microsatellite markers from the 18q21 region. Obligate recombinants in two families place the gene in a 7-cM interval, between markers D18S69 and D18S64. All intervening markers had significant LOD scores in two-point linkage analysis. Moreover, we identified one family in which the BRIC gene seems to be unlinked to the 18q21 region, or that represents incomplete penetrance of the BRIC genotype.

Iatrogenic neonatal hypertrophic cardiomyopathy

Transient hypertrophic cardiomyopathy is a rare sequela of both glucocorticoid and insulin excess. We report two ELBW infants who developed hypertrophic cardiomyopathy as an iatrogenic complication of the concurrent therapeutic administration of a glucocorticoid and insulin. In both cases the hypertrophic cardiomyopathy resolved completely on cessation of therapy. We advise caution when using this therapeutic combination and stress the need for regular echocardiography.

Artificial symbiogenesis

Symbiosis is the phenomenon in which organisms of different species live together in close association, resulting in a raised level of fitness for one or more of the organisms. Symbiogenesis is the name given to the process by which symbiotic partners combine and unify-forming endosymbioses and then potentially transferring genetic material-giving rise to new morphologies and physiologies evolutionarily more advanced than their constitutents. In this article we begin by using the NKC model of coevolution to examine endosymbiosis and its effect on the evolutionary performance of the partners involved. We are then able to suggest the conditions under which endosymbioses are more likely to occur and why; we find they emerge between organisms within a window of their respective "chaotic gas regimes" and hence that the association represents a more stable state for the partners. The conditions under which gene transfer is more likely to represent an advantage for such endosymbionts are then examined within the same model. We find that, providing a suitable pathway exists, such a process can lead to a more efficient genetic configuration for the symbionts within a window that overlaps that in which endosymbioses occur. Finally, the results are used as grounds for implementing symbiogenesis within artificial evolutionary multiagent systems.

Recombination of 4p16 DNA markers in an unusual family with Huntington disease

The Huntington disease (HD) mutation has been localized to human chromosome 4p16, in a 6-Mb region between the D4S10 locus and the 4p telomere. In a report by Robbins et al., a family was identified in which an affected individual failed to inherit three alleles within the 6-Mb region originating from the parental HD chromosome. To explain these results, it was suggested that the HD locus (HD) lies close to the telomere and that a recombination event took place between HD and the most telomeric marker examined, D4S90. As a test of this telomere hypothesis, we examined six members of this family, five of whom are affected with HD, for the segregation of 12 polymorphic markers from 4p16, including D4S169, which lies within 80 kb of the 4p telomere. We separated, in somatic cell hybrids, the chromosomes 4 from each family member, to determine the phase of marker alleles on each chromosome. We excluded nonpaternity by performing DNA fingerprint analyses on all six family members, and we found no evidence for chromosomal rearrangements when we used high-resolution karyotype analysis. We found that two affected siblings, including one of the patients originally described by Robbins et al., inherited alleles from the non-HD chromosome 4 of their affected parents, throughout the 6-Mb region. We found that a third affected sibling, also studied by Robbins et al., inherited alleles from the HD chromosome 4 of the affected parent, throughout the 6-Mb region. Finally, we found that a fourth sibling, who is likely affected with HD, has both a recombination event within the 6-Mb region and an additional recombination event in a more centromeric region of the short arm of chromosome 4. Our results argue against a telomeric location for HD and suggest that the HD mutation in this family is either associated with DNA predisposed to double recombination and/or gene conversion within the 6-Mb region or is in a gene that is outside this region and that is different from that mutated in most other families with HD.

A cloned DNA segment from the telomeric region of human chromosome 4p is not detectably rearranged in Huntington disease patients

Genetic linkage studies have mapped the Huntington disease (HD) mutation to the distal region of the short arm of human chromosome 4. Analysis of recombination events in this region has produced contradictory locations for HD. One possible location is in the region distal to the D4S90 marker, which is located within 300 kilobases of the telomere. Other crossover events predict a more centromeric position for HD. Here we analyze the telomeric region of 4p in detail. Cloned DNA segments were derived from this region by utilizing a radiation-induced somatic cell hybrid as a source of DNA combined with preparative pulsed-field gel electrophoresis to enrich for the telomeric fraction. Additional DNA was obtained by using the cloned segments as multiple start points for cosmid walks. This strategy proved to be an effective method for cloning 250 kilobases of DNA in the region telomeric to D4S90. Hybridization analysis with the cloned DNA did not provide any evidence for the presence of rearrangements of 100 base pairs or greater in the DNA of individuals affected with HD. We also found no change in the size or structure of the 4p telomere in these samples.