Search PubMed⌕ Search

Biomedical subjects

W Haas

Publications and source records attributed to W Haas.

At least 73 records · Page 4Linked to original sources
PubMed1991

Host-finding and host recognition of infective Ancylostoma caninum larvae.

A. caninum larvae responded to environmental and host stimuli with four behavioral phases of host-finding. (1) Snake-like movement was stimulated by warmth and by defined vibrations of the substratum. (2) Waving behavior was a prerequisite for the passive change-over to dog hairs. It was stimulated by heat radiation and by the CO2 content, warmth, and humidity of an air stream. (3) Creeping direction: the larvae were attracted by heat in temperature gradients as weak as 0.04 degrees C mm-1 and by dog hydrophilic skin surface extracts, but not by skin lipids or serum. (4) Penetration into agar was stimulated by heat, dog hydrophilic skin fraction, and dog serum. The effective component of serum had a molecular weight of between 5000 and 30,000 and proved to be a protein, since it lost its effectiveness after digestion with proteinases. Dog saliva, urine, milk, and various pure dog serum components did not stimulate penetration. A. caninum larvae were able to penetrate mouse skin repeatedly, but they did not follow the tracks of previously penetrated larvae in agar.

Ancylostoma↗
PubMed1991

Penetration of stimuli of fish skin for Acanthostomum brauni cercariae.

The cercaria of Acanthostomum brauni penetrates the skin of its fish host in response to a combination of two chemical signals from the fish skin surface: free fatty acids and a macro-molecular mucus component. The latter seems to be a protein, as the penetration-stimulating activity of fish skin surface mucus is eliminated by digestion with proteinase, but not by digestion with glycosidases, nor by a removal of glycosaminoglycans. These penetration-stimulating host signals differ from the glycoproteins that stimulate the attachment of A. brauni cercariae to the host and also from the macromolecular fish host signals which have been found to stimulate the attachment and penetration by Opisthorchis viverrini cercariae.

Animals↗
PubMed1991

Miracidia of Schistosoma japonicum: approach and attachment to the snail host.

Schistosoma japonicum miracidia swim directed along a chemical gradient toward the snails Oncomelania hupensis and Biomphalaria glabrata, and they turn back when the concentration of attractive chemicals decreases. The host signal for this chemotactic response has a molecular weight of more than 30,000. When swimming miracidia encounter the surface of O. hupensis or agar containing O. hupensis snail-conditioned water (SCW) they perform the host-specific responses "contact with return," "repeated investigation," and "attachment," but they do not exhibit such behavior when encountering B. glabrata surface or agar containing B. glabrata SCW. Thus S. japonicum miracidia respond to different host signals when they approach snails than when they attach to snails.

Animals↗
PubMed1990

Self-tolerance to transgenic gamma delta T cells by intrathymic inactivation.

During their intrathymic differentiation, T lymphocytes expressing alpha beta T-cell receptors (TCR) are negatively and positively selected. This selection contributes to the establishment of self-tolerance and ensures that mature CD4+ and CD8+ cell populations are restricted by the self major histocompatibility complex. Little is known, however, about gamma delta T-cell development. To investigate whether selection operates in the establishment of the gamma delta T-cell class, we have generated transgenic mice using gamma- and delta-transgenes encoding a TCR that is specific for a product of a gene in the TL-region of the TLb haplotype. Similar numbers of thymocytes expressing the transgenic TCR were generated in mice of TLb and TLd haplotypes. But gamma delta thymocytes from TLb and TLd transgenic mice differed in cell size, TCR density and in their capacity to respond to TLb stimulator cells or interleukin-2 (IL-2). In contrast to gamma delta T cells from TLd transgenic mice, gamma delta T cells from TLb transgenic mice did not produce IL-2 and did not proliferate in response to TLb stimulator cells, but they did proliferate in the presence of exogenous IL-2. These results indicate that functional inactivation of self-antigen-specific T cells could contribute to the establishment of self-tolerance to thymic determinants.

Animals↗
PubMed1990

Homing of a gamma delta thymocyte subset with homogeneous T-cell receptors to mucosal epithelia.

In mice gamma delta T-cell populations with distinct T-cell receptor (TCR) repertoires and homing properties have been identified. Diversified populations are found in lymphoid organs and intestinal epithelia. By contrast, the gamma delta T-cells that have been found in the murine skin are homogeneous. They express a TCR consisting of one particular V gamma 5 and one particular V delta 1 chain and seem to originate from early fetal thymocytes. We have now systematically analysed many tissues by immunohistochemistry and TCR gene sequencing aided by the polymerase chain reaction. These studies revealed a second homogeneous gamma delta T-cell subset in epithelia not of the intestine and skin, but of the vagina, uterus and tongue. The TCR expressed by this gamma delta T-cell subset consists of the same V delta 1 chain. Cells that express this particular TCR have previously been shown to be positively selected in the late fetal thymus.

Animals↗
PubMed1990

Finding and recognition of the bovine host by the cercariae of Schistosoma spindale.

The cercaria of Schistosoma spindale finds and identifies its bovine host with at least five behavioral phases. (1) Dispersal in and selection of midwater and water surface as the microhabitat are achieved by an intermittent swimming behavior with a weak geonegative but not photopositive orientation. (2) Attachments are stimulated by host-specific higher temperatures of the substrate but not by chemical host signals. (3) Remaining of the attached cercariae on the substrate is stimulated by host-specific higher temperatures of the substrate; chemical host signals have no effect. (4) The creeping of the cercariae is directed to the higher temperature in thermal gradients as weak as 0.07 degrees C/mm. Chemical gradients had no effect on the creeping direction. This behavior may enable the cercariae to migrate along hairs to the host's skin surface. (5) Penetrations are stimulated by the free fatty acid fraction of bovine skin-surface lipids. The characteristics of the stimulating fatty acids are the same as those identified for other schistosome species. Higher temperatures of the substrate alone do not stimulate penetrations. S. spindale cercariae do not use as many chemical host cues as stimuli for the identification of their host as do S. mansoni cercariae. S. spindale seems to be adapted to hairy hosts that are infected in shallow, muddy waters. The low host specificity of the cercarial host-finding behavior is compensated by an intimate parasite-snail intermediate host relationship, resulting in a high cercarial production of up to greater than 7,000 cercariae per snail per day.

Animals↗
PubMed1990

Opisthorchis viverrini: finding and recognition of the fish host by the cercariae.

The cercaria of Opisthorchis viverrini finds and recognizes its fish host by using at least four steps of behavioral patterns. (1) Dispersal and selection of plant-free water microhabitat are achieved by intermittent swimming behavior with positive phototactic orientation. (2) Attachment to the host is stimulated by water currents and a hydrophilic component of fish skin surface which has a molecular weight of more than 30,000. This component is sensitive to digestion with hyaluronidase and seems to be a glycosaminoglycan other than hyaluronic acid and chondroitin sulfate. (3) Remaining on the host's surface is induced by an unknown chemical component of fish skin surface mucus. (4) Penetration into the host is triggered by a hydrophilic component of fish skin surface of a molecular weight of more than 30,000. This host signal has a proteinaceus character as it is sensitive to proteinase digestion but not to hyaluronidase and glycosidases. The requirement of O. viverrini cercariae for complete glycosaminoglycans and proteins as signals in host identification may have the advantage that the numerous small molecules in mud and decaying materials in the water cannot interfere with host-finding.

Animals↗
PubMed1990

Positive selection of gamma delta T cells.

The issue of T-cell repertoire selection has been addressed recently by several laboratories. While evidence has been provided for both negative and positive selection of CD4+ and CD8+ alpha beta T cells, the molecular basis of positive selection remains unclear. In this article Juan Lafaille and colleagues describe molecular features of gamma delta T-cell selection in the fetal thymus. These features were deduced from extensive junctional sequence data of gamma delta T-cell receptor genes in fetal thymocytes. Their data suggest the active participation of a self peptide in the positive selection of gamma delta T cells.

Animals↗
PubMed1990

The development and function of gamma delta T cells.

In June of this year, a small group of researchers came together at the inspiring location of Segovia, Spain to exchange information and opinions on gamma delta T cells. In this report the new, unpublished findings presented, and the ideas that germinated during the meeting are discussed in the context of recent gamma delta literature.

Animals↗
PubMed1990

The complete sequence of the human beta-myosin heavy chain gene and a comparative analysis of its product.

We have isolated and sequenced the gene and the cDNA coding for the human cardiac beta-myosin heavy chain (designated MYH7). The gene is 22,883 bp long. The 1935 amino acids of this protein (Mr223,111) are encoded by 38 exons. The 5' untranslated region (86 bp) is split by two introns. The 3' untranslated region is 114 bp long. Three Alu repeats were identified within the gene and a fourth one in the 3' flanking intergenic region. The molecular organization of this gene reflects the conservative pattern with respect to size, coding ratio, and number or position of introns characteristic of vertebrate sarcomeric myosin heavy chain genes. The protein sequence of the human beta-heavy chain was compared with corresponding (homologous) sequences of rabbit, rat, and hamster as well as with the (heterologous) embryonic heavy chain sequences of rat, chicken, and man. The results show that protein subregions responsible for basic functions of myosin heavy chains (nucleotide binding and actin binding) are very similar in homologous and heterologous heavy chains. Regions that differ in their primary sequences in heterologous heavy chains appear to be highly conserved within mammalian beta-myosin heavy chains. Constant and variable subregions of heavy chains are discussed in terms of functional significance and evolutionary relatedness.

Amino Acid Sequence↗
PubMed1990

Poly- and monoclonal antibodies against recombinant rat brain calbindin D-28K were produced to map its selective distribution in the central nervous system.

Many processes in the CNS depend on calcium. The calcium signal is transduced into an intracellular response via Ca2(+)-binding proteins, including calbindin D-28K. In many laboratories, polyclonal antibodies against chicken intestinal calbindin D-28K have been used to study its localization in the brain (normal and degenerated) of various species, including humans, but some of these antisera cross-reacted with other proteins, including calretinin. We purified recombinant rat brain calbindin D-28K to raise antisera in rabbits and purified a recombinant rat-chicken calbindin D-28K hybrid protein to immunize mice for the generation of monoclonal antibodies. These antisera were highly specific for calbindin D-28K, as demonstrated by two-dimensional Western blotting analysis. Immunohistochemical analyses combined with in situ hybridization studies demonstrated that calbindin D-28K in the Purkinje cells of the cerebellum is independent of vitamin D. The antibodies described here will be important tools for studying the regulation of expression of calbindin D-28K and its biological function in the brain and in the PNS.

Animals↗
PubMed1990

Cyclic ovarian function in recreational athletes.

In 17 female recreational athletes, ovarian function was monitored using daily hormone measurements and serial ultrasound determinations. Whereas 11 out of 13 women of a control group showed estradiol (E2) maxima beyond 470 pmol/l, progesterone (P4) maxima of 19 nmol/l or more, and a luteal phase length of 9 days or more, only 10 out of 17 athletes satisfied these criteria. Six athletes showed disturbed follicular development, and one athlete showed luteal phase disturbance. Both athletes with disturbed menstrual function (n = 7) and athletes fulfilling the above-mentioned minimal criteria (n = 10) had lower E2 concentrations in all phases of the menstrual cycle (P less than 0.05). P4 concentrations were significantly decreased in the group with disturbed menstrual function (P less than 0.05). Maximal aerobic capacity in the two athlete groups was similar. Neither athlete group showed the expected increase in caloric intake compared with the sedentary controls. It is concluded that recreational running is associated with altered ovarian function. Inadequate nutritional adaptation may be a contributing factor.

Adult↗
PubMed1990

[Olfactory and gustatory sweating--case report on reflex facial hyperhidrosis].

Localised hyperhidrosis is comparatively rare among the vegetative disorders. A case of pathological gustatory and olfactory sudation is reported, with the sequence of symptoms corresponding to that of the Frey syndrome. Working from the reflex nature of the phenomen, the paper puts forward a model to account for the delayed onset of the manifestation following a peripheral lesion. It is assumed that readjustment of the reflex excitation level takes place according to a modification in peripheral afference, and that a decompensation of the central control mechanisms results in a pathological enhancement of the reflex. The hypothesis of peripheral efferentisl denervation hypersensitivity appears insufficient to account for the delay in manifestation, or even to account for the classic Frey syndrome following an affection of the parotid gland.

Humans↗
PubMed1990

[Acoustically evoked brain stem potentials in acute alcoholic intoxication].

Under the acute influence of alcohol with blood alcohol concentrations (BAK) ranging between 0.62 to 2.04%, the IPL prolongations of our subjects were within standard deviations compared with normal data. Depending on the BAK, these minor IPL alterations hint at a special vulnerability in the pontomesodiencephal area. The increase in BAK significantly correlates with the reduction of body temperature. The BAEP proves to be suitable for defining undear states of coma different origin.

Adult↗
PubMed1989

[Acoustically evoked brain stem potentials in chronic alcoholism and withdrawal].

BAEP studies hint at different neurophysiological findings between gamma and delta alcoholics. On the first day of withdrawal gamma alcoholics show slight vegetative withdrawal symptoms in the form of CNS hyperexitability trough the shortening of the early IPL. However delta alcoholics show prolongations of the late IPL which can be interpreted as a consequence of brain stem transmission disorders resulting from chronic intoxication. After four weeks the BAEP deviations found in both groups indicate a clear tendency of recovery which points to functional disorders.

Adult↗
PubMed1989

[Neurologic manifestations of Lyme borreliosis].

The authors report on recent concept of Lyme borreliosis. The disease is caused by Borrelia burgdorferi transmitted by tick bite. As with other spirochetal illnesses, Lyme borreliosis occurs in stages. The dermatological, rheumatological, cardiological and especially neurological aspects in the course of disease are described and the principles of immunodiagnosis and treatment are explained.

Diagnosis, Differential↗