Lower Mammals Research Articles

Serial segmental duplications during primate evolution result in complex human genome architecture

The human genome is particularly rich in low-copy repeats (LCRs) or segmental duplications (5%-10%), and this characteristic likely distinguishes us from lower mammals such as rodents. How and why the complex human genome architecture consisting of multiple LCRs has evolved remains an open question. Using molecular and computational analyses of human and primate genomic regions, we analyzed the structure and evolution of LCRs that resulted in complex architectural features of the human genome in proximal 17p. We found that multiple LCRs of different origins are situated adjacent to one another, whereas each LCR changed at different time points between >25 to 3-7 million years ago (Mya) during primate evolution. Evolutionary studies in primates suggested communication between the LCRs by gene conversion. The DNA transposable element MER1-Charlie3 and retroviral ERVL elements were identified at the breakpoint of the t(4;19) chromosome translocation in Gorilla gorilla, suggesting a potential role for transpositions in evolution of the primate genome. Thus, a series of consecutive segmental duplication events during primate evolution resulted in complex genome architecture in proximal 17p. Some of the more recent events led to the formation of novel genes that in human are expressed primarily in the brain. Our observations support the contention that serial segmental duplication events might have orchestrated primate evolution by the generation of novel fusion/fission genes as well as potentially by genomic inversions associated with decreased recombination rates facilitating gene divergence.

Low mammal and hornbill abundance in the forests of Barito Ulu, Central Kalimantan, Indonesia

Faunal surveys in Kalimantan have been biased towards primates in protected forests close to the coast. Relatively little has been documented on other animal species, particularly in the vast interior forests. The results of a 1996–97 census of nine large mammal and eight hornbill species in tropical lowland forest in Barito Ulu, Central Kalimantan are reported here. Pigs Sus barbatus had the highest biomass, but this was due to large numbers migrating through the study area over 4 months and the resident population is probably low. Langurs Presbytis rubicunda and hybrid gibbons Hylobates mulleri × agilis had the highest biomass of all resident species. Orang-utans Pongo pygmaeus were absent from the area during the study period and pig-tailed macaques Macaca nemestrina were rarely seen. The resident hornbill species (Anthracoceros malayanus, Anorrhinus galeritus, Buceros vigil and B. rhinoceros) had high densities compared to that reported from lowland areas, but overall hornbill density was low due to the absence of the nomadic Aceros corrugatus and A. undulatus, except during peak fruit abundance. Sun bears Helarctos malayanus, long-tailed macaques M. fascicularis, muntjacs Muntiacus spp. and mouse deer Tragulus spp. were at low densities. Density of two large squirrel species, Ratufa affinis and Sundasciurus hippiurus, was lower than has been reported in Sarawak, but the density of Prevost's squirrel Callosciurus prevostii was higher. We discuss hunting pressure, isolation, low abundance of large fruit trees, poor soils, and specific habitat preferences as possible explanations for the low mammal and hornbill density at Barito Ulu.

Prenatal exposure of Long–Evans rats to 17α-ethinylestradiol modifies neither latent inhibition nor prepulse inhibition of the startle reflex but elicits minor deficits in exploratory behavior

Prenatal administration of synthetic estrogens in humans as well as lower mammals was reported to alter behavior in adulthood. The alterations remain to be characterized according to specific pathophysiological hypotheses. In this study, three common behavioral models of schizophrenia were tested, i.e., latent inhibition (LI), prepulse inhibition of the startle response (PPI) and hyperlocomotion under amphetamine. Female Long–Evans rats were injected i.p. with a solution of 17α-ethinylestradiol (15 μg kg −1) everyday from day 9 to 14 of pregnancy, and behavioral characteristics of their offspring, raised by Wistar foster mothers, were compared to those of rats born from dams injected with the vehicle only, over the same gestation period. LI was tested in a conditioned taste aversion and a conditioned passive avoidance paradigm followed by a parametric study of PPI and an evaluation of locomotion in an open field under saline or amphetamine (1.5 mg kg −1). Histological brain measurements were also carried out in a subset of the same rats. Neither LI nor PPI was altered using methods that had proven sensitive in previous pharmacological studies. Treated rats' locomotion was impaired, but amphetamine did not elicit a differential enhancement. A thinner Amon's horn layer was observed in their hippocampus. This indicates that standard models of schizophrenia did not fit to the behavioral abnormalities found by others and confirmed in this study. They were not due to the abnormal maternal care to pups elicited by the treatment.

Transdifferentiation Potential of Ciliary and Pigment Epithelial Cells in Lower Vertebrates and Mammals

Cellular composition of the peripheral region of the eye in amphibians and mammals as well as embryonic fissure in amphibians was studied. Different distributions of proliferating cells in retinal pigment epithelium have been revealed in adult amphibians (newt, axolotl, and Xenopus). Single cells incorporated [3H]thymidine in the newt and Xenopus; 0.4% cells, in the axolotl. An embryonic fissure was observed in the eye of the axolotl. Pigment epithelial cells in the embryonic palpebral region actively proliferated: about 20% cells incorporated [3H]thymidine. Proliferating cells were also localized in the ciliary marginal zone of the retina in all studied amphibians, particularly, in the axolotl. In newborn hamsters, [3H]thymidine-labeled cells have been revealed in the pigment epithelium as well as in the outer pigmented and inner unpigmented layers of the ciliary body. Proliferative activity of the peripheral regions of the eye is due to eye growth in adult amphibians and newborn hamsters. After retinectomy, the retina is regenerated from the cells of the growth ciliary marginal zone in all amphibians, pigment epithelial cells in the newt, and pigment epithelial cells of the embryonic fissure in the axolotl. Heterogeneous composition of the pigment epithelium in the newt and axolotl reflects high transdifferentiation potential of these regions. Structural comparison of the peripheral region of the eye in amphibians and mammals demonstrate that the ciliary body of mammals containing stem cells is homologous to the ciliary marginal zone of amphibians containing multipotent cells.

Human babesiosis – an unrecorded reality: Absence of formal registry undermines its detection, diagnosis and treatment, suggesting need for immediate mandatory reporting

Human babesiosis, caused by parasitic protozoa of erythrocytes, has escaped usual associates – lower mammals. Thriving in tick guts, it has spread inland from the coasts of America, adopting mankind as a host. Babesia spp. threaten life quality of unsuspecting humans in quickly expanding territories worldwide, including the state of Pennsylvania, USA. The causative spirochetes of Lyme disease often similarly co-exist in ticks. Singly or together they may, by causing persistent and chronic infections, duplicate any symptom in the medical literature – including depression and hypochondriasis. Physicians practicing throughout Pennsylvania have identified patients with symptomatic babesiosis, but without governmental surveillance or health registries that require doctors to consider and report babesiosis, these cases have not prompted epidemiological concern. Misunderstandings such as, “Isn't that an obscure tropical disease?” are usual responses when doctors are asked about babesiosis, inadvertently trivializing patients and disease. Mandatory reporting of babesiosis should now be considered a medical necessity.

Sleep-Dependent θ Oscillations in the Human Hippocampus and Neocortex

Hippocampal theta waves recorded during rapid eye movement (REM) sleep are thought to play a critical role in memory consolidation in lower mammals, but previous attempts to detect similar theta oscillations in the human hippocampus have been unsuccessful. Using subdural and depth recordings from epileptic patients, we now report the first evidence of state-dependent hippocampal theta waves (4-7 Hz) in humans. Unlike the continuous theta in rodents, however, these oscillations were consistently observed during REM sleep in short (approximately 1 sec) bursts and during transitions to wake in longer epochs. Theta waves were also observed in the basal temporal lobe and frontal cortex during transitions from sleep to wake and in quiet wakefulness but not in REM, and they were not coherent with hippocampal theta oscillations. The absence of functional coupling between neocortex and hippocampus during theta periods indicates that multiple theta generators exist in the human brain, and that they are dynamically regulated by brain state. Gamma oscillations were also present during REM theta bursts, but the fluctuations in gamma power were not associated with theta phase, pointing out another significant difference between rodent and human theta properties. Together, these findings suggest that the generation mechanisms of theta oscillations in humans might have evolved from tonic to phasic in hippocampus during REM sleep and extended from hippocampus to cortex, where they appear in certain wakefulness-related states.

Structural and functional maturation of the developing primate brain

Descriptive studies have established that the developmental events responsible for the assembly of neural systems and circuitry are conserved across mammalian species. However, primates are unique regarding the time during which histogenesis occurs and the extended postnatal period during which myelination of pathways and circuitry formation occur and are then subsequently modified, particularly in the cerebral cortex. As in lower mammals, the framework for subcortical-cortical connectivity in primates is established before midgestation and already begins to remodel before birth. Association systems, responsible for modulating intracortical circuits that integrate information across functional domains, also form before birth, but their growth and reorganization extend into puberty. There are substantial differences across species in the patterns of development of specific neurochemical systems. The complexity is even greater when considering that the development of any particular cellular component may differ among cortical areas in the same primate species. Developmental and behavioral neurobiologists, psychologists, and pediatricians are challenged with understanding how functional maturation relates to the evolving anatomical organization of the human brain during childhood, and moreover, how genetic and environmental perturbations affect the adaptive changes exhibited by neural circuits in response to developmental disruption.

Decrease of human pancreatic cancer cell tumorigenicity by alpha1,3galactosyltransferase gene transfer.

The enzyme alpha1,3galactosyltransferase synthesizes the alphaGal epitope, a carbohydrate structure (Galalpha1,3Galbeta1,4GlcNAc-R), on glycoconjugates in lower mammals. The enzyme is absent in humans but large amounts of natural antibodies that recognize alphaGal epitopes are present in human serum. It is likely that these antibodies contribute to the host defense and participate in the hyperacute rejection of xenograft. Previous studies indicated that the glycosyltransferase gene transfer into tumoral cells can modify the structure of glycoconjugates at the cell surface and, as a consequence, modulates the metastatic and tumorigenic behaviors of these cells. The aim of our study was to determine whether the expression of alphaGal epitope can modify the tumorigenicity of human pancreatic cancer cells. The expression of alphaGal epitopes in the human pancreatic cancer cell lines BxPC-3 and Panc-1 was obtained by selecting stable cell clones transfected with murine alpha1,3galactosyltransferase gene. The expression of the enzyme activity in BxPC-3 and Panc-1 cells resulted in the formation at the cell surface of alphaGal epitopes that are recognized by human anti-alphaGal antibodies. alphaGal epitope expression at the surface of pancreatic cancer cells was associated with the fixation of complement 1q to human anti-alphaGal antibodies. The alphaGal epitope expression also resulted in a delay in the tumoral development of BxPC-3 and Panc-1 cells in vivo after xenograft transplantation of nude mice. In addition to the impairment of the metastatic potential of murine tumor cell lines and the activation of immune response, our study provides evidence that the cell surface expression of alphaGal epitopes also modulates the tumorigenic behavior of human pancreatic cancer cells.

Personality trait of behavioral inhibition is associated with oscillatory systems reciprocal relationships

The main aim of this paper is to offer a speculative evolutionary based interpretation of brain oscillations. We suppose that delta, theta and alpha oscillations are informational channels of three hierarchical philogenetic systems. Delta oscillations are linked with the most ancient system, which was dominant in reptilian brain. Theta oscillations dominate in lower mammals. Alpha oscillations are manifestation of activity of the newest system, which dominate in adult humans. The three hierarchical phylogenetic systems fulfill parallel processing and their contribution to resulting behavior could differ in different individuals. Relative contribution of each system is regulated by means of descending inhibition (DI), higher systems inhibiting the lower. One of this theory's implications is that the personality trait of behavioral inhibition (behavioral inhibition system, BIS) should be associated with a stronger DI but particular mechanism could be different in children and adults. In order to test this hypothesis in 95 children (11–16 years) and 45 adults (18–37 years) resting EEG recordings were obtained along with BIS scores assessed by the Gray–Wilson Personality Questionnaire. Within subject strength of DI was measured by negative correlations between delta, theta and alpha powers estimated in individually adjusted EEG bands. In adults, BIS was associated with enhanced negative feedback from the alpha to the delta system, indicating a predominantly cortical origin of the adult humans’ anxiety. In children, BIS was associated with enhanced negative relation between theta and delta systems, which is similar to the mechanism known in animals where limbic system plays the crucial role in mediating anxiety and fear. Although the presented empirical data partly supported the theory, it remains to be speculative and needs further empirical validation.

Brain development and the onset of mood disorders.

Research in mood disorder pathophysiology has stimulated considerable interest in clinical and biologic aspects of mood disorders among children and adolescents. From the clinical perspective, developmental aspects of psychiatric disorders have crystallized in the relatively new theoretical school known as developmental psychopathology. This school attempts to understand the nature of developmental changes in behavior, with the goal of differentiating normal from abnormal stage-related behavior. This perspective has exerted major impact on conceptualizations of psychiatric disorders. From the basic science perspective, biologic findings in emotion have stimulated an integration of basic and clinical approaches to mood disorders. The term emotion is often used to refer to brain states elicited by stimuli for which an organism will extend effort to obtain (rewards) or avoid (punishments). Imaging studies suggest that brain regions engaged by rewarding and punishing stimuli in lower mammals are also implicated in mood disorders. Other studies suggest that environmental factors exert profound effects on the development of these brain regions. The impact of 4 areas of research on our understanding of depression pathophysiology is reviewed: (1) mood disorder onset, (2) structural magnetic resonance imaging (MRI), (3) behavioral or cognitive correlates of major depression, and (4) functional MRI of brain regions engaged across development. This is a US government work. There are no restrictions on its use.

Compositional patterns in reptilian genomes

Sauropsids form a complex group of vertebrates including squamates (lizards and snakes), turtles, crocodiles, sphenodon and birds (which are often considered as a separate class). Although avian genomes have been relatively well studied, the genomes of the other groups have remained only sparsely characterized. Moreover, the nuclear sequences available in databanks are still very limited. In the present study, we have analysed the compositional patterns, i.e. the GC (molar fraction of guanine and cytosine in DNA) distributions, of 31 reptilian (particularly snake) genomes by analytical ultracentrifugation of DNAs in CsCl gradients. The profiles were characterized by their modal buoyant density ρ o, mean buoyant density 〈 ρ〉, asymmetry 〈 ρ〉− ρ o, and heterogeneity H. The modal buoyant density distribution of reptilian DNAs clearly distinguishes two groups. The snakes fall in the same range of modal densities as most mammals, whereas crocodiles, turtles and lizards show higher values (>1.700 g/cm 3). As far as the more important compositional properties of asymmetry and heterogeneity are concerned, previous studies showed that amphibians and fishes share relatively low values, whereas birds and mammals are characterized by highly heterogeneous and asymmetric patterns (with the exception of Muridae, which have a lower heterogeneity). The present results show that the snake genomes cover a broad range of asymmetry and heterogeneity values, whereas the genomes of crocodiles and turtles cover a narrow range that is intermediate between those of fishes/amphibians and those of mammals/birds.

Hormonal regulation of spermatogenesis in primates and man: insights for development of the male hormonal contraceptive.

A better understanding of the hormonal regulation of spermatogenesis may provide new avenues for management of human infertility, and development of safe and reversible contraceptives. Although much basic work must be conducted in lower mammals, primarily rodents, concepts must, at some stage, be tested for their relevance to humans. In this review, we will draw together existing data in humans and monkeys in formulating an overview of the hormonal regulation of spermatogenesis, focusing particularly on the pursuit of the male hormonal contraceptive. Reference to data from lower mammals will be made when these highlight interesting and relevant differences or similarities with primates. The dual functions of the adult testis; namely, the production of spermatozoa (fertility) and the secretion of testosterone (virility), are both dependent on stimulation by the pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are secreted in response to hypothalamic gonadotropin-releasing hormone (GnRH). Testosterone is essential for promoting spermatogenesis and is secreted by the adult Leydig cell under LH stimulation, and acts via androgen receptors (ARs) on Sertoli cells, Leydig cells, and peritubular cells. That testosterone exerts its effects on somatic cells rather than germ cells was highlighted by recent germ cell transplantation studies (Johnston et al, 2001). FSH acts via

The beta1 integrin subunit is not a specific component of the costamere domain in human myocardial cells.

Studies on altered integrin receptor expression during cardiac hypertrophy and heart failure requires accurate knowledge of the distributional pattern of integrins in myocardial cells. At present the general consensus is that in cardiac muscle the beta1 integrin receptor is mainly localized to the same sarcolemmal domain as vinculin at Z-band levels ('costamere'). Since most previous studies have been focusing on myocardial integrin distribution in lower mammals, the myocardial localization of the beta1 integrin subunit was investigated in biopsies collected from the auricle of patients undergoing a coronary bypass operation. Non-invasive serial optical sectioning was carried out by immuno-laser scanning confocal microscopy. Double-labelling for vinculin/alpha-actinin, and the cytoplasmic domain for the beta1 integrin subunit, showed that beta1 integrin is deposited throughout both the vinculin/alpha-actinin domains and the non-vinculin/alpha-actinin domains. These results were supported by a semi-quantitative analysis in extended focus images of the latter preparations. Higher magnification views at the electron microscopical levels of the large, extracellular domain of the beta1 integrin subunit disclosed a pronounced labelling in the form of a dense, irregular punctuate pattern that was distributed at Z-disc domains as well as along the entire sarcolemmal area between Z-discs. Our findings show that in human, myocardial cells, the beta1 integrin receptor does not only localize to the surface membrane at the Z-disc level ('costamere' in cardiac muscle), but has a widespread distribution along the sarcolemma.

Unipolar brush cells in the human cochlear nuclei identified by their expression of a metabotropic glutamate receptor (mGluR2/3)

Unipolar brush cells (UBCs) reside in the mammalian vestibulo-cerebellum and the ventral (VCN) and, particularly, dorsal cochlear nuclei (DCN). Human cerebellar UBCs are numerous too, but auditory UBCs have escaped detection. The human DCN, considered a degenerated structure, lost lamination and possibly neurons common in lower mammals, like UBCs. We searched for human auditory UBCs probing their immunoreactivity against the calcium-binding protein calretinin (CR-IR), and a metabotropic glutamate receptor (mGluR2/3-IR). We found: UBCs are constituents of the human DCN and VCN, though in small numbers. These auditory UBCs are not CR-IR, in contrast to human cerebellar UBCs and cerebellar and auditory UBCs in non-primate mammals, but display mGluR2/3-IR. The human DCN, thus, appears more complete than previously thought. This may be of interest regarding auditory brainstem electrode implantations in deaf patients.

Cyclic oscillations in melanin composition within hairs of baboons.

The wild-type agouti-banding pattern for hair is well characterized in lower mammals such as mice. The switch between eumelanin and pheomelanin in bands in the hair results from the interaction of alpha-melanocyte stimulating hormone and agouti signal protein through the melanocortin 1 receptor on melanocytes. However, such banding patterns have not been described to date in higher mammals. We now report such 'agouti'-banding patterns that occur in several subspecies of baboons, and characterize those hairs using chemical and immunohistochemical methods. Hair and skin samples were obtained from the dorsa of adult male baboons of different subspecies (Papio cynocephalus hamadryas (PCH) and Papio cynocephalus anubis (PCA)). The hairs were excised with scissors into the gray and the white bands of the PCH subspecies and into the black and the yellow bands of the PCA subspecies, and were analyzed for total melanin, eumelanin, and pheomelanin by spectrophotometric and chemical methods. Hairs in the PCA subspecies oscillate between a eumelanic band (with high melanin content) and a pheomelanic band, while hairs in the PCH subspecies oscillate between a eumelanic band (with low melanin content) and a non-pigmented band. Those chemical data are consistent with the histological appearance of the hair bulbs stained by the Fontana-Masson technique. The difference in the melanin content between PCH and PCA subspecies is most likely related to tyrosinase levels, as suggested by the presence of unpigmented muzzle in the PCH subspecies compared with the black muzzle in the PCA subspecies.

Protection of myelin basic protein immunized mice from free-radical mediated inflammatory cell invasion of the central nervous system by the natural peroxynitrite scavenger uric acid

Peroxynitrite (ONOO −), the product of nitric oxide (NO ) and superoxide (O 2 − ), is believed to be a major contributor to immunotoxicity when produced by activated cells expressing inducible nitric oxide synthase (iNOS). Uric acid (UA) is a natural scavenger of ONOO − that is present at high levels in the sera of humans and other higher order primates relative to most lower mammals. We have previously shown that UA treatment is therapeutic in experimental allergic encephalomyelitis (EAE), a rodent model of multiple sclerosis (MS). In this study we have examined the effect of UA therapy on the dynamics of the appearance of iNOS-positive cells in central nervous system (CNS) tissue of mice subjected to the stimuli that cause EAE. The results indicate that UA prevents activated monocytes from entering CNS tissue where they may contribute to the pathogenesis of MS and other CNS diseases.

Naturally occurring anti-alpha-galactosyl antibodies: relationship to xenoreactive anti-alpha-galactosyl antibodies.

Antibodies produced by an individual without a known history of sensitization to the relevant antigen are called "natural" antibodies. Some natural antibodies, called xenoreactive antibodies, react with the cells of foreign species. Most xenoreactive antibodies in humans and higher primates bind to a nonreducing terminal galactose expressed by pigs and other lower mammals. Although human natural antibodies which bind to one or more of a variety of terminal alpha-galactosyl structures have been identified previously, the antigen recognized by anti-alpha-galactosyl antibodies on the cells of foreign species is thought to be exclusively Galalpha1-3Gal. Thus, anti-alpha-galactosyl antibodies which do not react with Galalpha1-3Gal are thought to be nonxenoreactive. Here, we identify natural antibodies in human serum which bind to Galalpha1-6Hexosepyrranosides but not Galalpha1-3Gal, indicating that these antibodies are not xenoreactive. Various lower mammals were found to have natural anti-Galalpha1-2Gal antibodies in their sera, suggesting that at least some anti-Galalpha1-2Gal antibodies might not be xenoreactive and indicating, surprisingly, that anti-alpha-galactosyl antibodies are much more phylogenetically disperse than previously known. Also surprising was the finding that some natural antibodies which bind to Galalpha1-3Gal in vitro do not bind to porcine xenografts. These studies show that naturally occurring anti-alpha-galactosyl antibodies in mammalian serum include antibodies with a greater variety of reactivities than previously thought, only some of which would bind to a porcine xenograft. Further, these studies show that the methods used to detect anti-alpha-galactosyl antibodies of relevance in xenotransplantation must be carefully evaluated to avoid detection of anti-alpha-galactosyl antibodies which would not bind to a porcine organ and which therefore are not involved in xenograft rejection.

Tolerance by transplantation: how much is enough, how much is too much?

In 1900, Ehrlich and Morgenroth observed that the infusion of foreign hematopoietic cells into goats elicited a potent immune response, whereas the infusion of autologous cells did not. They speculated that “the organism possesses certain contrivances by means of which the immunity reaction, so easily produced by all kinds of cells, is prevented from working against the organism’s own elements” (1). These contrivances, known collectively as immunological tolerance, are now defined as the absence of an immune response against a specific antigen or cell after a sufficient immune stimulus is given. The tolerant individual should be fully able to mount a response to all other antigens. The idea that specific immune unresponsiveness might reflect an acquired biological condition was surmised by Owen in 1945 (2). Owen observed that dizygotic twins of cattle have hematopoietic stem cells of both twins in the circulation, owing presumably to their exchange of hematopoietic stem cells (2), a striking observation given the immunogenicity of hematopoietic precursors by the twin fetuses (3). Billingham et al. deliberately induced hematopoietic chimerism in fetal and newborn animals, thereby demonstrating that tolerance induced by chimerism allows the permanent engraftment of skin from the hematopoietic cell donor (4). Why would foreign hematopoietic cells in Ehrlich’s goats give rise to immunity, while foreign hematopoietic cells in Owen’s cattle give rise to tolerance? The simplest answer is that the fetal immune system is poised for the induction of tolerance, whereas the mature immune system is poised for the induction of immunity. This answer is not entirely satisfactory, however, because the fetus can respond immunologically to certain antigens (e.g., transplacental infections give rise to specific IgM antibodies) and because in mature individuals the repertoire of lymphocytes, being continuously regenerated, must be subject to ongoing induction of tolerance under conditions in which immunity might be induced. An alternative view, then, is that foreign hematopoietic cells stimulate tolerance in developing lymphocytes and immunity or immune regulation (deletion, anergy, or suppression) in mature lymphocytes. In mature individuals, it is the balance of tolerance, immunity, and immune regulation that dictates the intensity and duration of the response. Several investigators have recently reported that the administration of bone marrow cells expressing Galα1-3Gal into lethally irradiated Gal-deficient mice induces tolerance to Gal (5, 6). Galα1-3Gal is a saccharide expressed by lower mammals but not by humans and higher primates. Species that do not express this sugar have natural anti–Galα1-3Gal antibodies that are thought to initiate the rejection of vascularized xenografts (7). Given the intensity of humoral responses to Galα1-3Gal, it is postulated that tolerance to this sugar might contribute to the clinical application of xenotransplantation (8, 9). In this issue of the JCI, Ohdan et al. report that tolerance to Galα1-3Gal can be induced by hematopoietic chimerism (10). To investigate tolerance by chimerism, Ohdan infused wild-type murine bone marrow cells expressing Galα1-3Gal into mice that do not express αGal because of targeted disruption of the gene encoding α1,3-galtransferase (α1,3GT), the enzyme that catalyzes synthesis of Galα1-3Gal. These mice, like humans, make antibodies against Galα1-3Gal. To allow engraftment of foreign bone marrow cells, the α1,3GT mice were treated with a sublethal dosage of whole-body irradiation and with anti–T cell antibodies. The treated mice accepted the bone marrow grafts, had a notable reduction of anti–Galα1-3Gal antibodies, and did not reject subsequently implanted Galα1-3Gal+ hearts. If it is not the first report on the induction of tolerance to Gal by hematopoietic chimerism (5, 6), why should Ohdan’s work warrant attention and commentary? The answer is that this report begins to explore what may be more important questions: how much tolerance is enough, and how much is too much.

Major carbohydrate epitopes in tissues of domestic and African wild animals of potential interest for xenotransplantation research.

We investigated the main glycotopes expressed on the tissues of 44 animal species, including primates, nonprimate mammals, marsupials, birds, and a reptile. Paraffin-embedded tissue sections of kidney, heart, liver, pancreas, lung, brain and intestine of 24 domestic animal species were stained with seven fluorescent-labeled lectins. Testis sections of 20 African wild animal species were tested with the same lectins. Overall, three main immunofluorescence patterns were found in the vascular compartment. First, humans and Old World monkeys express genetically polymorphic ABH antigens and do not express alphaGal. Second, New World monkeys, other mammals, and marsupials do not express ABH antigens, but have large amounts of a genetically monomorphic alphaGal. Third, birds and reptiles do not express either ABH or alphaGal, but have monomorphic betaGal, probably different from the lactosamine precursor of ABH and alphaGal. Epithelial cells producing exocrine secretions also expressed carbohydrate epitopes. The fluorescence patterns of the cells of the exocrine compartment are similar, but not identical, to those expressed in the vascular compartment. All the animals tested have some ABH and betaGal in exocrine tissues, but New World monkeys and lower mammals are the only ones expressing alphaGal in exocrine tissues.

Secular and seasonal changes in semen quality among young Danish men: a statistical analysis of semen samples from 1927 donor candidates during 1977-1995.

The objective of this study was to investigate whether semen quality has changed during the years 1977-1995 in a group of unselected semen donor candidates, and to determine whether semen quality is subject to seasonal variation, by analysis of time- and season-related changes in semen quality using multiple regression and ANOVA. The study was based on analysis of the first semen sample delivered by 1927 semen donor candidates in Copenhagen during the period 1977-1995, with determination of semen volume, sperm concentration, total sperm count, percentage motile spermatozoa, and a semiquantitative sperm motility score. Multiple linear regression analysis with year, sexual abstinence and season as covariates showed a significant increase in mean sperm concentration from 53.0 x 10(6)/mL in 1977 to 72.7 x 10(6)/mL in 1995 (p < 0.0001) and in mean total sperm count from 166.0 x 10(6) to 227.6 x 10(6) (p < 0.0001). Mean semen volume and percentage motile spermatozoa did not change. Sperm motility deteriorated, as the spermatozoa in 74.2% of the samples were of excellent motility in 1977-1980 compared to only 41.9% in 1993-1995 (chi 2 = 130.0, p < 0.0001). Analysis of variance showed significant variation between seasons regarding sperm concentration (p < 0.0001) and total sperm count (p < 0.0001). Highest sperm counts were found in spring, with a mean concentration (95% C.I.) of 77.6 x 10(6)/mL (71.9-83.7), and lowest in summer, with a mean of 57.5 x 10(6)/mL (50.1-65.4). No other semen parameter varied with season. It is concluded that sperm counts increased, whereas sperm motility decreased, in a group of Danish semen donor candidates, from 1977 to 1995. Due to the retrospective design and the anonymity of the donors, we were unable to control for variation in donor age, and we cannot exclude the possibility that some donor candidates were selected by being accepted as donors by other semen donor services in Copenhagen. With these limitations in mind, we suggest our results should be interpreted cautiously and regarded as a contribution to the ongoing dispute on whether or not there is a continuous decrease in sperm quality. The seasonal variations found in sperm concentration and total sperm count were pronounced and were not attributable to seasonal differences in the length of sexual abstinence. Additionally, the same seasonal pattern was observed in five successive year-intervals. These findings strongly indicate that human testicular function is influenced by season, a phenomenon well known in many lower mammals.