Premature cardiovascular disease in chronic renal failure

There is a remarkable lack of reliable information about the determinants of risk of cardiovascular disease (CVD) among patients with chronic renal failure. Indeed, such patients have often been deliberately excluded from randomised trials of treatments of CVD, perhaps because of concerns about drug safety. But the absolute risk of CVD among them may be large, so the potential absolute benefits of treatments may also be large, and may well exceed any increased hazards. Hence, as well as further investigation of the underlying mechanisms of cardiac disease, it would be helpful to have some large-scale randomised trials in a wide range of renal patients of interventions (such as cholesterol-lowering drugs, antihypertensives, aspirin, B-vitamins, and antioxidant vitamins) that are of proven or suspected benefit in other settings. If safe and effective treatments can be identified, and started early in the natural history of renal failure, the exceptionally high risk of CVD experienced by these patients could be decreased before and after end-stage renal failure has occurred.

The Pseudomonas aeruginosa quorum-sensing signal molecule N-(3-oxododecanoyl)-L-homoserine lactone has immunomodulatory activity

Diverse gram-negative bacterial cells communicate with each other by using diffusible N-acyl homoserine lactone (AHL) signal molecules to coordinate gene expression with cell population density. Accumulation of AHLs above a threshold concentration renders the population "quorate," and the appropriate target gene is activated. In pathogenic bacteria, such as Pseudomonas aeruginosa, AHL-mediated quorum sensing is involved in the regulation of multiple virulence determinants. We therefore sought to determine whether the immune system is capable of responding to these bacterial signal molecules. Consequently the immunomodulatory properties of the AHLs N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) and N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) were evaluated in murine and human leukocyte immunoassays in vitro. OdDHL, but not OHHL, inhibited lymphocyte proliferation and tumor necrosis factor alpha production by lipopolysaccharide-stimulated macrophages. Furthermore, OdDHL simultaneously and potently down-regulated the production of IL-12, a Th-1-supportive cytokine. At high concentrations (>7 x 10(-5) M) OdDHL inhibited antibody production by keyhole limpet hemocyanin-stimulated spleen cells, but at lower concentrations (<7 x 10(-5) M), antibody production was stimulated, apparently by increasing the proportion of the immunoglobulin G1 (IgG1) isotype. OdDHL also promoted IgE production by interleukin-4-stimulated human peripheral blood mononuclear cells. These data indicate that OdDHL may influence the Th-1-Th-2 balance in the infected host and suggest that, in addition to regulating the expression of virulence determinants, OdDHL may contribute to the pathogenesis of P. aeruginosa infections by functioning as a virulence determinant per se.

The role of nourishment in oogenesis

Oogenesis in insects is typically a nutrient-limited process, triggered only if sufficient nourishment is available. This nourishment can be acquired during the larval or adult stage, depending on the insect. Timing of food intake will have major effects on mechanisms of hormonal control. When nourishment for eggs is taken primarily by adults, insufficient nutrition inhibits egg development through mechanisms such as inhibition of corpora allata, as seen in Orthoptera and Blattaria. In adult Diptera, lack of protein inhibits release of brain factors that produce reproductive competency or ovarian stimulation. Lepidoptera have been characterized as lacking substantial regulation of oogenesis because egg development is underway at emergence. Many species for which ecological data are available do not mobilize reserves carried over from the larval stage until they feed as adults. The endocrine mechanisms underlying these systems are poorly understood. In many insects, mating and activity can affect nutritional state and therefore oogenesis. Mating can stimulate oogenesis through mobilization of reserves or through nutritional contributions by males to females. Activity, especially flight, and oogenesis can compete for energy. The flight apparatus, especially the muscle, can also compete with oogenesis for protein. Social insects exhibit extreme specializations in oogenesis; females range in fertility from completely sterile to hyperfecund. Food flow within colonies is a major factor regulating fecundity. Finally, maternal nourishment is not needed for oogenesis in parasitoids and pseudoplacental viviparous insects, which produce eggs with little or no yolk. Virtually nothing is known about the endocrine regulation of oogenesis on these insects.

Influenza vaccine effectiveness in preventing hospitalizations and deaths in persons 65 years or older in Minnesota, New York, and Oregon: data from 3 health plans

This study developed methods and determined the impact of influenza vaccination on elderly persons in 3 large health plans: Kaiser Permanente Northwest, HealthPartners, and Oxford Health Plans. Data for the 1996-1997 and 1997-1998 seasons were extracted from administrative databases. Subjects were health plan members > or = 65 years old. Comorbid conditions collected from the preceding year were used for risk adjustment with logistic regression. The virus-vaccine match was excellent for year 1 and fair for year 2. Both years, during peak and total periods, vaccination reduced all causes of death and hospitalization for pneumonia and influenza: hospitalizations were reduced by 19%-20% and 18%-24% for years 1 and 2, respectively, and deaths were reduced by 60%-61% and 35%-39% for the same periods. These results show that all elderly persons should be immunized annually for influenza. The methods used in this study are an efficient cost-effective way to study vaccine impact and similar questions.

Nurse management of patients with minor illnesses in general practice: multicentre, randomised controlled trial

OBJECTIVE

To assess the acceptability and safety of a minor illness service led by practice nurses in general practice.

DESIGN

Multicentre, randomised controlled trial.

SETTING

5 general practices in south east London and Kent representing semi-rural, suburban, and urban settings.

PARTICIPANTS

1815 patients requesting and offered same day appointments by receptionists.

INTERVENTION

Patients were assigned to treatment by either a specially trained nurse or a general practitioner. Patients seen by a nurse were referred to a general practitioner when appropriate.

MAIN OUTCOME MEASURES

The general satisfaction of the patients as measured by the consultation satisfaction questionnaire. Other outcome measures included the length of the consultation, number of prescriptions written, rates of referral to general practitioners, patient's reported health status, patient's anticipated behaviour in seeking health care in future, and number of patients who returned to the surgery, visits to accident and emergency, and out of hours calls to doctors.

RESULTS

Patients were very satisfied with both nurses and doctors, but they were significantly more satisfied with their consultations with nurses (mean (SD) score of satisfaction 78.6 (16. 0) of 100 points for nurses v 76.4 (17.8) for doctors; 95% confidence interval for difference between means -4.07 to -0.38). Consultations with nurses took about 10 minutes compared with about 8 minutes for consultations with doctors. Nurses and doctors wrote prescriptions for a similar proportion of patients (nurses 481/736 (65.4%) v doctors 518/816 (63.5%)). 577/790 (73%) patients seen by nurses were managed without any input from doctors.

CONCLUSION

Practice nurses seem to offer an effective service for patients with minor illnesses who request same day appointments.

Antibiotics and surgery for vesicoureteric reflux: a meta-analysis of randomised controlled trials

AIMS

To evaluate the benefits and harms of treatments for vesicoureteric reflux in children.

METHODS

Meta-analyses of randomised controlled trials using a random effects model. Main outcome measures were incidence of urinary tract infection (UTI), new or progressive renal damage, renal growth, hypertension, and glomerular filtration rate.

RESULTS

Eight trials involving 859 evaluable children comparing long term antibiotics with surgical correction of reflux (VUR) and antibiotics (seven trials) and antibiotics compared with no treatment (one trial) were identified. Risk of UTI by 1-2 and 5 years was not significantly different between surgical and medical groups (relative risk (RR) by 2 years 1.07; 95% confidence interval (CI) 0.55 to 2.09, RR by 5 years 0.99; 95% CI 0.79 to 1.26). Combined treatment resulted in a 60% reduction in febrile UTI by 5 years (RR 0.43; 95% CI 0.27 to 0.70) but no concomitant significant reduction in risk of new or progressive renal damage at 5 years (RR 1.05; 95% CI 0.85 to 1.29). In one small study no significant differences in risk for UTI or renal damage were found between antibiotic prophylaxis and no treatment.

CONCLUSION

It is uncertain whether the identification and treatment of children with VUR confers clinically important benefit. The additional benefit of surgery over antibiotics alone is small at best. Assuming a UTI rate of 20% for children with VUR on antibiotics for five years, nine reimplantations would be required to prevent one febrile UTI, with no reduction in the number of children developing any UTI or renal damage.

Excursion and strain of the median nerve

Five fresh-frozen transthoracic cadaver specimens (ten upper extremities) were dissected in order to measure excursion and strain of the median nerve at the wrist and the elbow in association with different positions of the shoulder, elbow, wrist, and fingers. The relationships between motions of the joints and excursion and strain at the wrist and the elbow as well as between excursion and strain were also determined. When the wrist was moved from 60 degrees of extension to 65 degrees of flexion, the median nerve at the wrist underwent a mean total excursion of 19.6 millimeters (9.2 +/- 1.38 millimeters [mean and standard deviation] in extension and 10.4 +/- 1.50 millimeters in flexion). The change in strain was not measurable secondary to nerve-wrinkling. Motion of the fingers from hyperextension to full flexion caused a mean total excursion of 9.7 millimeters (6.3 +/- 1.31 millimeters in hyperextension and 3.4 +/- 1.04 millimeters in flexion) and a change in strain of 19.0 per cent. This change in strain became more pronounced when the wrist and the fingers moved in synergy. Such strain, if constant, has been shown to decrease microvascular perfusion and nerve conduction in rabbits. With motion of the shoulder, the mean total excursion of the median nerve at the elbow was 9.1 millimeters (4.4 +/- 1.64 millimeters in abduction and 4.7 +/- 1.81 millimeters in adduction) and the change in strain was 13.3 per cent. With motion of the elbow, the mean total excursion was 12.3 millimeters (12.3 +/- 4.20 millimeters in flexion and zero millimeters in the resting position) and the change in strain was not measurable because of the wrinkle effect in flexion. With motion of the wrist, the mean total excursion was 5.6 millimeters (4.3 +/- 1.95 millimeters in extension and 1.25 +/- 0.81 millimeters in flexion) and the change in strain was 14.8 per cent. With motion of the fingers, the mean total, excursion was 3.4 millimeters (2.6 +/- 1.13 millimeters in hyperextension and 0.80 +/- 0.92 millimeter in flexion) and the change in strain was 10.3 per cent. Motion of the wrist and the fingers induced profound excursion of the median nerve at the wrist, whereas motion of the shoulder and the elbow induced marked excursion of the median nerve at the elbow. These excursions were much more pronounced when a number of joints were moved in a composite manner. Any factor that might limit normal excursion, such as scarring, could induce strains that could adversely affect the function of the median nerve. The finding that the position and movement of the limb had a profound effect on excursion and strain of the median nerve at the wrist and the elbow may aid in the understanding of the pathophysiology of median-nerve neuropathy.

Medical management of spinal epidural abscesses: case report and review

Although the traditional management of spinal epidural abscesses includes antibiotic therapy and surgical drainage, numerous reports have appeared in the literature that describe a nonsurgical approach. We report the successful nonsurgical management of a case of an extensive spinal epidural abscess in which the patient was closely monitored by serial studies with magnetic resonance imaging. Review of the literature from 1970 to 1990 revealed 37 cases that describe conservative management of spinal epidural abscesses. Despite successful conservative management reported for some cases, sudden neurological deterioration of patients receiving appropriate antibiotic therapy has also occurred. A true index of the success of nonsurgical therapy is difficult to discern since cases may have been selectively reported and unsuccessful attempts at conservative management may have never been reported once a laminectomy was performed. A prospective investigation that includes clearly defined indications for conservative management vs. surgical intervention and that can be studied with an intention-to-treat analysis is needed.

Indoor air quality for poor families: new evidence from Bangladesh

Poor households in Bangladesh depend heavily on wood, dung and other biomass fuels for cooking. This paper provides a detailed analysis of the implications for indoor air pollution (IAP), drawing on new 24-h monitoring data for respirable airborne particulates (PM10). A stratified sample of 236 households was selected in Dhaka and Narayanganj, with a particular focus on fuel use, cooking locations, structural materials, ventilation practices, and other potential determinants of exposure to IAP. At each household, PM10 concentrations in the kitchen and living room were monitored for a 24-h period during December, 2003-February, 2004. Concentrations of 300 microg/m3 or greater are common in our sample, implying widespread exposure to a serious health hazard. A regression analysis for these 236 households was then conducted to explore the relationships between PM10 concentrations, fuel choices and a large set of variables that describe household cooking and ventilation practices, structure characteristics and building materials. As expected, our econometric results indicate that fuel choice significantly affects indoor pollution levels: natural gas and kerosene are significantly cleaner than biomass fuels. However, household-specific factors apparently matter more than fuel choice in determining PM10 concentrations. In some biomass-burning households, concentrations are scarcely higher than in households that use natural gas. Our results suggest that cross-household variation is strongly affected by structural arrangements: cooking locations, construction materials, and ventilation practices. A large variation in PM10 was also found during the 24-h cycle within households. For example, within the 'dirtiest' firewood-using household in our sample, readings over the 24-h cycle vary from 68 to 4864 microg/m3. Such variation occurs because houses can recycle air very quickly in Bangladesh. After the midday meal, when ventilation is common, air quality in many houses goes from very dirty to reasonably clean within an hour. Rapid change also occurs within households: diffusion of pollution from kitchens to living areas is nearly instantaneous in many cases, regardless of internal space configuration, and living-area concentrations are almost always in the same range as kitchen concentrations. By implication, exposure to dangerous indoor pollution levels is not confined to cooking areas. To assess the broader implications for poor Bangladeshi households, we extrapolate our regression results to representative 600 household samples from rural, peri-urban and urban areas in six regions: Rangpur in the north-west, Sylhet in the north-east, Rajshahi and Jessore in the west, Faridpur in the center, and Cox's Bazar in the south-east. Our results indicate great geographic variation, even for households in the same per capita income group. This variation reflects local differences in fuel use and, more significantly, construction practices that affect ventilation. For households with per capita income <US Dollars 1.00/day, rural PM10 concentrations vary from 410 microg/m3 in Cox's Bazar to 202 microg/m3 in Faridpur. In urban areas, concentrations for such households differ by almost 100 microg/m3 between the highest areas, Jessore and Rajshahi, and the lowest, Sylhet. Practical Implications Our analysis suggests that poor families may not have to wait for clean fuels or clean stoves to enjoy significantly cleaner air. Within our sample household population, some arrangements are already producing relatively clean conditions, even when 'dirty' biomass fuels are used, such as simple changes in ventilation characteristics of housing (construction materials, space configurations, cooking locations and placement of doors and windows) and ventilation behavior (keeping doors and windows open after cooking). As these arrangements are already within the means of poor families, the scope for cost-effective improvements may be larger than is commonly believed.

The effects of femoral intramedullary reaming on pulmonary function in a sheep lung model

Two methods of intramedullary fixation of fractures of the middle of the femoral shaft were evaluated in a sheep model to determine the effect of femoral reaming on pulmonary function. The effect of a modified reamer was also studied. A second experiment with the same model was performed to evaluate the relationship between embolization and pulmonary dysfunction. This experiment involved two groups of sheep--those with normal lungs and those with contused lungs--divided into subgroups--those that had nailing with reaming and those that had nailing without reaming. Intracardiac ultrasound was used to measure the magnitude and duration of transvenous particulate embolization during the operations. Both experiments involved hemodynamic monitoring during and after the nailing. The pulmonary tissue was examined histologically after the animals were killed. The hemodynamic monitoring revealed only a transient increase in pulmonary vascular resistance in the animals that had femoral nailing with reaming in both experiments. The modified reamer had no effect on the pulmonary response. Histological analysis of pulmonary tissue demonstrated a significant increase in the number of fat emboli in both the animals that had nailing with reaming and the animals that had nailing without reaming compared with the control animals. Intravascular ultrasound revealed that the operative maneuver associated with the greatest number of emboli was opening of the intramedullary canal with the awl. The first two passes of the reamer produced more emboli and embolism of longer duration than did the later passes. Pulmonary confusion did not increase the risk of pulmonary dysfunction due to intramedullary nailing in this model.

Can we imagine how objects look from other viewpoints?

Many psychologists who study cognition believe that perception achieves object-centered representations that make it possible to extract representations of how the object would appear from differing viewpoints. Others believe we can achieve representations of how an object would appear by a process of visualization or mental rotation. We report experiments in which the subject tries to imagine how three-dimensional novel wire objects would appear from positions other than the one they are in. Subjects are unable to perform this task unless they make use of strategies that circumvent the process of visualization. It is suggested that the linear increase in time required to succeed in mental rotation tasks as a function of the angular discrepancy between the figures compared is the result of increasing difficulty rather than of the time required for rotation.

Intravenous immunoglobulin-induced osmotic nephrosis

Intravenous immunoglobulin preparations are being used for an increasing number of indications in clinical medicine. To minimize adverse reactions, sugar additives such as sucrose are added to some preparations to serve as stabilizing agents. We describe a patient treated with an immunoglobulin preparation containing sucrose who developed a fully reversible form of acute renal failure with histologic changes characterized by vacuolization and swelling of renal proximal tubular cells. We believe the high concentration of sucrose in the immunoglobulin preparation resulted in osmotic injury to the renal tubules. Such changes, which are identical to those described in humans and experimental animals given intravenous infusions of hypertonic sucrose, have come to be known as osmotic nephrosis. Risk factors for the development of this lesion are renal insufficiency and volume depletion. The risk for such injury can be minimized by further diluting the immunoglobulin preparation and slowing the infusion rate.

Potent small molecule inhibitors of spleen tyrosine kinase (Syk)

A series of oxindoles demonstrating inhibition of the phosphorylation of biotinylated substrates of Syk and IgE/Fc epsilon RI triggered basophil cell degranulation has been identified. A study of the SAR around sulfonamide 31 (IC(50)=5 nM, EC(50)=1400 nM) is discussed. The modest cellular activity representative of the sulfonamide series was overcome when the Polar Surface Area was lowered to <110 A(2), leading to the identification of amide 32 (IC(50)=145 nM, EC(50)=100 nM).

Incidence of ligament lesions and associated degenerative changes in the elderly wrist

The scapholunate, lunotriquetral, and triangular fibrocartilage of 62 cadaveric wrists were examined to determine the incidence of pathologic changes in asymptomatic elderly wrists. A scapholunate ligament lesion was noted in 18 wrists; the majority of defects were incomplete and involved the central portion of the ligament only. Lunotriquetral ligament defects were noted in 20 wrists; eight were partial defects, most of them were central ligament lesions. Triangular fibrocartilage defects were present in 33 wrists and consisted of two distinct patterns: a central oval pattern with actual tissue loss and a linear defect running in the dorsal anterior direction 2-3 mm ulnar to the radial attachment of the triangular fibrocartilage. X-ray film evaluation showed few significant degenerative changes with no pronounced collapse deformities. Defects involving the scapholunate, lunotriquetral, or triangular fibrocartilage were very common, with the presence of at least one of these ligament defects in wrists. These ligament defects occur as a process of aging and behave in a manner quite different from traumatic lesions of these same structures in the younger population.

Phylogenetic and structural analyses of MMTV LTR ORF sequences of exogenous and endogenous origins

The long terminal repeat (LTR) of mouse mammary tumor virus (MMTV) harbors an open reading frame (ORF) that encodes a glycoprotein and is present in all exogenous and endogenous MMTV proviruses. The ORF protein has been reported to interact with the immune system of mice to cause deletion of specific V beta-bearing subsets of T cells. Twenty-two MMTV LTR ORF sequences were analyzed. Although highly conserved, the MMTV ORF sequences are not identical, with approximately 35% of the total variation clustered at the carboxy terminus. Statistical analysis revealed the presence of two conserved regions in the protein, one of which contained a transmembrane-like domain (residues 45-63). Two potential nuclear localization signals were recognized. Many ORF sequences shared polymorphisms. To analyze relationships, phylogenetic trees were constructed on the basis of alignments of LTR ORF sequences. A tree generated from the carboxy-terminal 35 residues clustered the sequences into three divergent families. The topology of the tree based on the amino-terminal 288 residues differed significantly, with some MMTV sequences rearranged relative to their carboxy-terminal families. A continuum of exogenous-like to endogenous-like character was suggested by the amino-terminal tree. The discordance between the topologies of the two trees suggests that some type of genetic exchange has occurred in the MMTV LTR gene. Mechanisms and implications of such genetic exchange are discussed.

The role of N-methyl-D-aspartate receptors in the regulation of physiologically released dopamine

In vivo voltammetry was used to measure changes in ascorbate, which are an index of changes in the release of glutamate, and microdialysis was used to measure changes in dopamine in the striatum of freely moving rats. A 5 min tail pinch produced a rapid rise in striatal ascorbate paralleled by an increase in motor activity and a slower, more prolonged rise in dopamine. Systemic administration of ketamine or dizocilpine maleate, non-competitive antagonists of the N-methyl-D-aspartate glutamate receptor, produced an increase in the basal level of ascorbate but not dopamine; however, the tail pinch-evoked rise in both ascorbate and dopamine was completely abolished by these drugs. The rise in dopamine was also abolished by local infusion of dizocilpine maleate into the striatum. Local application of N-methyl-D-aspartate produced a dose-dependent increase in dopamine, which was partially reduced in the presence of tetrodotoxin. The results show that the tail pinch-evoked increase in motor activity involves an increase in the release of striatal dopamine which requires the activation of N-methyl-D-aspartate receptors in the striatum. This suggests that phasic increases in striatal dopamine release are triggered by the action of glutamate on dopaminergic nerve terminals.

Differential effects of everyday stress on the episodic memory test performances of young, mid-life, and older adults

This research explored the differential association of everyday stress with the episodic memory test performances of young, mid-life, and older adults. Participants included 98 community-dwelling adults ranging in age from 19-89 years. Everyday stress was assessed via the Perceived Stress Scale and the Elder Life Stress Inventory. A brief battery of episodic memory tasks was administered which included tests of Logical Memory, Verbal Paired Associates, Digit Symbol Substitution, and Digit Symbol Incidental Learning. Results suggest that everyday hassles and irritations as well as the accumulation of challenging life events may exacerbate age-related decline on episodic memory tests that require greater executive resources and more integrated and elaborative processing. The functional relationship between affective status and risk for dementia is discussed, and consideration of individual differences in everyday stress is suggested so as to allow more sensitive interpretation of episodic memory tests commonly used to discern mild cognitive impairment.

An orphaned mammalian beta-globin gene of ancient evolutionary origin

Mammals possess multiple, closely linked beta-globin genes that differ in the timing of their expression during development. These genes have been thought to be derived from a single ancestral gene, by duplication events that occurred after the separation of the mammals and birds. We report the isolation and characterization of an atypical beta-like globin gene (omega-globin) in marsupials that appears to be more closely related to avian beta-globin genes than to other mammalian beta-globin genes, including those previously identified in marsupials. Phylogenetic analyses indicate that omega-globin evolved from an ancient gene duplication event that occurred before the divergence of mammals and birds. Furthermore, we show that omega-globin is unlinked to the previously characterized beta-globin gene cluster of marsupials, making this the first report of an orphaned beta-like globin gene expressed in a vertebrate.

Reconstruction of the humerus with an intramedullary fibular graft. A clinical and biomechanical study

Nine patients with nonunited humeral shaft fractures were treated by open reduction and internal fixation with an intramedullary fibular bone graft and a compression plate. Fixation of the screws was enhanced by passing them through the fibula as well as the two humeral cortices (quadricortical fixation). Eight of the nine fractures united at an average of 3.5 months. Tests on cadaver bones showed that quadricortical fixation was as strong as methylmethacrylate augmentation and significantly better than bicortical fixation.

Generalized lymphadenopathy and T cell abnormalities in hemophilia A

Two patients with hemophilia A had generalized lymphadenopathy, lymphopenia, elevated IgG values, depressed T4 (helper) lymphocytes, elevated T8 (suppressor) lymphocytes, and abnormally low T4/T8 ratios. One of the patients, who also had hepatosplenomegaly, underwent cervical lymph node biopsy; the node contained 43% T8-lymphocytes, a marked elevation over the small fraction of T8 cells usually found in lymph nodes. These patients may have a form of the acquired immune deficiency syndrome described in male homosexuals, Haitians, intravenous drug abusers, and recently, in patients with hemophilia. We studied T cell phenotypes in 43 patients with hemophilia. Fourteen of 28 patients given commercial factor VIII concentrates had abnormal T4/T8 ratios; none of nine patients who used cryoprecipitate had abnormal values. T4 helper cells were significantly lower, T8 suppressor cells significantly elevated, and T4/T8 ratios significantly lower in the lyophilized concentrate users and in patients with hemophilia as a total group. The type of therapeutic factor VIII replacement may alter the risk of developing T4/T8 abnormalities or AIDS.

Kallmann syndrome gene on the X and Y chromosomes: implications for evolutionary divergence of human sex chromosomes

The recently identified gene for X-linked Kallmann syndrome (hypogonadotropic hypogonadism and anosmia) has a closely related homologue on the Y chromosome. The X and Y copies of this gene are located in a large region of X/Y homology, on Xp22.3 and Yq11.2, respectively. Comparison of the structure of the X-linked Kallmann syndrome gene and its Y homologue shed light on the evolutionary history of this region of the human sex chromosomes. Our data show that the Y homologue is not functional. Comparative analysis of X/Y sequence identity at several loci on Xp22.3 and Yq11.2 suggests that the homology between these two regions is the result of a complex series of events which occurred in the recent evolution of sex chromosomes.