Possible Role of Malaria in the Aetiology of the Nephrotic Syndrome in Nairobi

In a study in Nairobi, Kenya, 30 young adults with nephrotic syndrome were investigated in detail and a further 18 were studied less completely. In no case was evidence found to support a possible role for malaria in the aetiology of the syndrome.     

Cranial cartilages: Players in the evolution of the cranium during evolution of the chordates in general and of the vertebrates in particular

The present contribution is chiefly a review, augmented by some new results on amphioxus and lamprey anatomy, that draws on paleontological and developmental data to suggest a scenario for cranial cartilage evolution in the phylum chordata. Consideration is given to the cartilage-related tissues of invertebrate chordates (amphioxus and some fossil groups like vetulicolians) as well as in the two major divisions of the subphylum Vertebrata (namely, agnathans, and gnathostomes). In the invertebrate chordates, which can be considered plausible proxy ancestors of the vertebrates, only a viscerocranium is present, whereas a neurocranium is absent. For this situation, we examine how cartilage-related tissues of this head region prefigure the cellular cartilage types in the vertebrates. We then focus on the vertebrate neurocranium, where cyclostomes evidently lack neural-crest derived trabecular cartilage (although this point needs to be established more firmly). In the more complex gnathostome, several neural-crest derived cartilage types are present: namely, the trabecular cartilages of the prechordal region and the parachordal cartilage the chordal region. In sum, we present an evolutionary framework for cranial cartilage evolution in chordates and suggest aspects of the subject that should profit from additional study.     

Role of spermatogonia in the stage-synchronization of the seminiferous epithelium in vitamin-A-deficient rats

After 20-day-old rats are placed on a vitamin-A-deficient diet (VAD) for a period of 10 weeks, the seminiferous tubules are found to contain only Sertoli cells and a small number of spermatogonia and spermatocytes. Retinol administration to VAD rats reinitiates spermatogenesis, but a stage-synchronization of the seminiferous epithelium throughout the testis of these rats is observed. In order to determine which cell type is responsible for this synchronization, the germ cell population has been analyzed in whole mounts of seminiferous tubules dissected from the testes of rats submitted to the following treatments. Twenty-day-old rats received a VAD diet for 10 weeks and then were divided into three groups of six rats. In group 1, all animals were sacrificed immediately; in group 2, the rats were injected once with retinol and sacrificed 3 hr later; in group 3, the rats were injected once with retinol, placed on a retinol-containing diet for 7 days and 3 hr, and then sacrificed. Three rats from each group had one testis injected with 3H-thymidine 3 hr (groups 1 and 2) or 7 days and 3 hr (group 3) before sacrifice. Three normal adult rats (approximately 100 days old) served as controls. Labeled and unlabeled germinal cells were mapped and scored in isolated seminiferous tubules. In group 1, type A1 and type A0 spermatogonia as well as some preleptotene spermatocytes were present; type A2, A3, A4, In, and B spermatogonia were completely eliminated from the testis. Neither type A1 mitotic figures nor 3H-thymidine-labeled-type A1 nuclei were seen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selenocysteyl-tRNA occurs in the diatom Thalassiosira and in the ciliate Tetrahymena

Selenocysteyl-tRNAs that decode UGA were identified previously in animal and bacterial cells and the genes for these tRNAs have been shown to be widespread in animals and eubacteria. In the present study, we identify a selenocysteyl-tRNA that codes for UGA in Thalassiosira pseudonana, which is a diatom, and in Tetrahymena borealis, which is a ciliate. The fact that these very diverse unicellular organisms also contain a selenocysteyl-tRNA suggests that selenocysteine-containing proteins and the use of UGA as a codon for selenocysteine are widespread, if not ubiquitous, in nature.     

On Sexual Apathy in the Male

Ever since World War II, there has been a noticeable change in the sexual behavior and responses in men and women. Women, in general, are becoming sexually more assertive and demanding and men more indifferent and lethargic. In patients of middle age, sexual boredom is particularly pronounced in men, whereas the post-menopausal female becomes more interested in sexual pleasure.In the youth of the “cool” generation, both boys and girls are quite open about sex, but their sexual activities precede emotional involvement. The similarities in dress and behavior of both sexes indicate a wish for a twin rather than a search for a lover. In the age group between 25 and 45, women demand equal orgasms since they have become economically independent and are relatively free of the fear of pregnancy. This seems to have mobilized a deep-seated unconscious fear and hatred of women in the male, making him sexually apathetic. In both sexes there is a growing alienation between romantic love and sex.     

Progress in application of the image analysing system QUANTIMET 720 in the histomorphometry of the microcirculatory system

The application of automated image analysing methods in the field of histomorphometry has been improved in the last decades. In this paper a new method is presented for the investigation of morphological reactions of the microcirculatory system. It is based on the measurement of quantitative changes in microvessel wall tissue by using the image analysing system QUANTIMET 720. In the measurement model, a microvessel intersection figure is considered as an ellipsis. A procedure is presented allowing the estimation of the wall and lumen area of the microvessel section and the calculation of its radius for a totally collapsed state. From this data, further morphometric parameters are derived. Using this method, the analysis of 500 microvessels including classification and parameter derivation takes about 10 min.     

Orientation in the dark: brain circuits involved in the perception of electric signals in mormyrid electric fish.

Weakly electric fish produce electric signals with a specialised organ in their tail. In addition, they are electrosensitive and can perceive their self-generated signals (for electrolocation) and electric signals of other electric fishes (for electrocommunication). Mormyrids possess three types of peripheral electroreceptor organs, one used for electrocommunication and two types involved in electolocation. They are innervated by afferent fibres, which project to different zones in the electrosensory lateral line lobe (ELL) in the medulla. Brain circuits for electrolocation and electrocommunication are separated almost throughout the whole brain. Electrolocation pathways run from the ELL-cortex to the torus semicircularis of the midbrain and then via the valvula cerebelli towards the telencephalon. Pathways involved in electrocommunication run from the nucleus of the ELL to another part of the torus and from there through the isthmic granule nucleus to the valvula. In addition, a pathway via the preglomerular complex to the telencephalon might exist. In both the electrolocation and the electrocommunication circuits, prominent recurrent pathways are present.     

Threshold results in the study of schistosomiasis

In a four-population model for schistosomiasis, the effect of the introduction of a trace of infection is considered. In particular, we are interested in whether the disease establishes itself or dies out quickly. Threshold results are presented for both the deterministic and the stochastic treatment of the model.     

Play and Its Role in the Mental Development of the Child

The problem of communication and its significance for cognition is a perpetual one in psychology. In making the problem of communication an object of study in psychology, investigators have always, to some extent, been aware of the role of dialogue as a cardinal factor in communication. Appreciation of the organizing and system-forming functions of dialogue (external or internal) in any process of communication and cognition has now grown steadily for a number of decades. In recent years, however, the role of dialogue in interconnected processes of communication and cognition has assumed a fundamentally new quality. A number of factors are responsible for this.     

Muscimol dialysis in the retrotrapezoid nucleus region inhibits breathing in the awake rat.

Under anesthesia, inactivation of the retrotrapezoid nucleus (RTN) region markedly inhibits breathing and chemoreception. In conscious rats, we dialyzed muscimol for 30 min to inhibit neurons of the RTN region reversibly. Dialysis of artificial cerebrospinal fluid had no effect. Muscimol (1 or 10 mM) significantly decreased tidal volume (VT) (by 16-17%) within 15 min. VT remained decreased for 50 min or more, with recovery by 90 min. Ventilation (VE) decreased significantly (by 15-20%) within 15 min and then returned to baseline within 40 min as a result of an increase in frequency. This, we suggest, is a compensatory physiological response to the reduced VT. Oxygen consumption was unchanged. In response to 7% CO(2) in the 1 mM group, absolute VE and change in VE were significantly reduced (by 19-22%). In the 10 mM group, the response to dialysis included a time-related increase in frequency and decrease in body temperature, which may reflect greater spread of muscimol. In the awake rat, the RTN region provides a portion of the tonic drive to breathe, as well as a portion of the response to hypercapnia.     

Teaching and training in geriatric medicine in the European Union

In 1993 about 20% of the population in the 15 'old' member countries of the European Union (EU) was over 60 years of age and this percentage will increase to more than 25% in 2020. These developments play a key role for the investments in education and training to meet societies needs for health care services. In 2002 about 25% of the medical students in the 'old' EU did not receive any education in geriatric medicine. A question is who will provide the services for older people in related areas, like social care, community care, acute care in the hospitals, long-term care, permanent care and care for psychiatric patients? Geriatric medicine has been recognized as an independent specialty in 8 of the 15 member countries of the 'old' EU. In all EU member states the governments are autonomous regarding all aspects of health care services, including the recognition of specialties and specialist training programmes. A two years training in internal medicine has been recommended in the EU, followed by another four years of training in geriatric medicine. The specialist training has a hospital oriented character, however, it includes also community care and other institutionalised care like nursing homes. The curriculum should contain: biological, social, psychological and medical aspects of common diseases and disturbances in older people. A problem in many EU countries is the shortage of well trained researchers and leading persons for academic positions for geriatric medicine. In a number of countries chairs at the universities remain vacant for long periods of time or even disappear. Good services in the health care for older people need a high quality curriculum and training programme.     

Variations in the Size of Mitotic Cells in the Root Meristem

Variations in the length of mitotic and interphase cells were analyzed in various tissues of wheat roots and in the cortex of maize roots. Reliable differences were shown in the length of mitotic cells in individual file clones of cells of the same tissue. The mean lengths of dividing cells in different roots differed to a lesser extent than those of different files in the same tissue of one root. Within the file, the length of the sister simultaneously dividing cells differed the least, while the difference of lengths of the neighbor simultaneously dividing nonsister cells was bigger. The mean length of interphase cells in any file was always less than that of mitotic cells by a factor of 1.45. This ratio was almost invariable for files and tissues in both the plants we studied and corresponded to that of an exponentially growing cell population. In addition, a very small number of cells were found (less than 1%) in meristems, which are longer than the mitotic cells. The length of these cells exceeded those of mitotic cells by less than twice. The origin of such cells is discussed. The length of mitotic cells near the quiescent center is more variable than in the middle of the meristem in the cortex of both plants. In the meristem basal part, the mitotic cells were no longer than those in the middle of the meristem but there were no small dividing cells. In the wheat epidermis, the cells are differentiated into trichoblasts and atrichoblasts and, therefore, the length of the dividing cells is highly variable. The cell length is essential for their transition to mitosis for all studied proliferating meristem cells.     

Sexual differences in the ependyma lining the third ventricle in the area of the anterior hypothalamus of adult rhesus monkeys

Summary Previous studies have shown that a circumscribed region of the anterior hypothalamus of the rhesus monkey is lined by tanycyte ependyma and it has been suggested that this ependyma which links the third ventricle with the pars tuberalis may have a functional role in the hypothalamic regulation of anterior pituitary function (Anand Kumar and Knowles, 1967a). In view of the known sexual differences in the hypothalamic regulation of pituitary gonadotropin secretion the present investigation was made to determine whether any structural differences were evident in the tanycyte ependyma in male and female rhesus monkeys.The results of this investigation are based on light and electron microscopic studies of the hypothalamus in 24 rhesus monkeys comprising 12 adult females, 11 sexually mature males and a two month old sexually immature male.The tanycyte ependyma in the rhesus monkey is double layered. There are bulbous projections on the ventricular surface of the cells in the ependymal layer nearest to the ventricle (the first layer of ependyma). These bulbous projections vary in size in relation to the menstrual cycle. They are well developed during mid-cycle and regressed during menstruation. In the males, where the secretion of pituitary gonadotropins does not occur cyclically as in the females, there was no marked variation in the bulbous projections between different individuals as in the female monkeys.In the sexually mature males, but not in the females, the two layers of ependyma are separated by a distinct space. The absence of such a space in the sexually immature male suggests that this difference may be related to sexual maturity.In the adult males the cells in the ependymal layer below the first layer of ependyma have microvilli which extend into the space between the ependymal layers. In the females where such a space is not present, microvilli were not evident.The precise functional significance of the tanycyte ependyma is not known. It is hoped that the results of the present investigation would draw attention to the need for a more detailed examination of the physiological role of the tanycyte ependyma in relation to reproduction.The expenses for this investigation were met from a grant made by the Ford Foundation to Professor Sir Solly Zuckerman and the electron microscope was provided by the Medical Research Council. I am indebted to Sir Solly for his interest in this work.     

Variations in the size of mitotic cells in the root meristem

Variations in the length of mitotic and interphase cells were analyzed in various tissues of wheat roots and in the cortex of maize roots. Reliable differences were shown in the length of mitotic cells in individual files-clones of cells of the same tissue. The mean lengths of dividing cells in different roots differed to a lesser extent than those of different files in the same tissue of one root. Within the file, the length of sister simultaneously dividing cells differed the least, while the difference of lengths of neighbor simultaneously dividing nonsister cells was bigger. The mean length of interphase cells in any file was always less than that of mitotic cells by a factor of 1.45. This ratio was almost invariable for files and tissues in both plants we studied and corresponded to that of an exponentially growing cell population. In addition, a very small number of cells were found (less than 1%) in meristems, which are longer than the mitotic cells. The length of these cells exceeded those of mitotic cells by less than twice. The origin of such cells is discussed. The length of mitotic cells near the quiescent center is more variable than in the middle of the meristem in the cortex of both plants. In the meristem basal part, the mitotic cells were no longer than those in the middle of the meristem but there were no small dividing cells. In the wheat epidermis, the cells are differentiated into trichoblasts and atrichoblasts and, therefore, the length of dividing cells is highly variable. The cell length is essential for their transition to mitosis for all studied proliferating meristem cells.     

Modeling in the museum: On the role of remnant models in the work of Joseph Grinnell

Accounts of the relation between theories and models in biology concentrate on mathematical models. In this paper I consider the dual role of models as representations of natural systems and as a material basis for theorizing. In order to explicate the dual role, I develop the concept of a remnant model, a material entity made from parts of the natural system(s) under study. I present a case study of an important but neglected naturalist, Joseph Grinnell, to illustrate the extent to which mundane practices in a museum setting constitute theorizing. I speculate that historical and sociological analyses of institutions can play a specific role in the philosophical analysis of model-building strategies.     

Knowledge and power in the clinical setting

In this paper we consider the three categories offered by Howard Brody for understanding power in medicine. In his book, The Healer's Power Brody separates out power in medicine into the categories of Aesculapian, Social, and Charismatic power. We examine these three categories and then apply them to a case. In this case set in an Obstetric ward, a junior member of the medical staff makes a clinical decision about a patient. This clinical decision is overruled by a senior medical staff member who then carries out his plan with disastrous consequences for the woman and her baby. This case challenges the three categories of power offered by Brody and highlights the need for a further category of Hierarchical power to be added to Brody's framework. We conclude by suggesting that there is a need to recognise the discrepancy in power not only between physician and patient but also between senior and junior staff in a clinical setting.     

On the Segregation of the Germ and Somatic Cell Lines in the Embryo

Abstract. In this paper we argue that the mechanisms underlying the segregation of the somatic and germ cell lines are basically similar. The interaction of the genome with specific cytoplasmic factors is responsible for the restriction of their developmental potencies in the somatic cell lines, and for the prevention of such a restriction in the germ cell line. In particular, it is suggested that meiosis is part of the differentiation program of the germ cells.     

Circumfacial Markings in Siamang and Evolution of the Face Ring in the Hylobatidae

The occurrence of a white brow band in siamang is documented for the first time. The characteristic occurs in 4.4% of 250 siamang. Among adult siamang the characteristic occurs more often in females than in males (11.3% of 71 females vs. 1.4% of 73 males). In a particular family lineage of captive siamang (not included in the numbers above), the characteristic was unusually frequent (42.9% of 14). The trait appears to be inherited, possibly as an autosomal dominant inheritance. Additional white markings occur in at least one of the subjects on hands, feet, and in a corona above the ears. In contrast to other studies, our results suggest that the presence of white facial markings, and possibly also of white hands and feet and of a bright corona are primitive gibbon traits. In addition, some degree of sexual dichromatism in the circumfacial markings appears to have occurred in the common ancestor of all gibbons.     

Trends in the BVDV serological response in the Upper Midwest.

Bovine viral diarrhoea continues to be an important disease affecting both beef and dairy animals of all ages. One of the quickest means of measuring bovine viral diarrhoea virus (BVDV) exposure and infection in the herd is a serum neutralization (SN) assay. Type 1 and type 2 BVDV SN results from the Animal Disease Research and Diagnostic Laboratory at South Dakota State University were collected over a seven-year period (1995-2001) to determine any trends. These results indicated that in 1996, 31% of the animals had titres > or =512 while in 2001, 74% of the titres were > or = 512. There has been a progressive increase over the seven-year period in the number of cases with titres > or = 512 with the exception of 1999 when there was a slight decrease. When analyzing the titres greater than 512, a further increase was seen. In 1995, 80% of the titres were < or = 1024 and 20% were 2048 and no titres were >2048. In 2001, 47% of the antibody levels were < or = 1024 while 53% were < or =2048 and 30% were >4096. The most dramatic increase in titres occurred in 1997 and the percentage of animals with titres from 512-8192 has remained fairly constant for the last five years (1997-2001). This increase is in part due to more extensive use of vaccination but probably also reflects a rise in field infections. In the future, standardizing existing BVDV SN serology along with developing new BVDV serology methods is necessary to provide continuity for any full-scale eradication programme.     

Cadherins in the mammary gland and the melanocyte lineage

Cadherins are transmembrane glycoproteins involved in cell-cell adhesion, signalling, proliferation and differentiation. In this review, we have focused upon in vivo cadherin expression and function in two different biological systems, the mammary gland epithelium and the melanocyte lineage. Development of the mammary gland represents a paradigm of in situ epithelial differentiation and the melanocyte lineage of a model of non-epithelial (or mesenchymal) cell differentiation where cells migrate extensively from their site of origin towards the skin compartment. In the mammary epithelium, the predominantly expressed cadherin is E-cadherin, a cell surface molecule that directs morphogenesis and maintenance of the epithelial structure. In the melanocyte lineage, the expression of a number of cadherins is strictly spatiotemporally regulated during development and adult life. The specific functions mediated by this very dynamic cadherin expression are not yet known and their characterisation represents a challenge for the future.