Medical biology最新文献

Colloidal gold particles are the markers of choice for ultrastructural localization of antigens. By reducing gold chloride with tannic acid and trisodium citrate, a broad range of narrowly determined particle sizes can be obtained. Such particles can easily be coupled to a number of proteins and the resulting conjugates are conveniently purified on a gel-chromatography column. Their application in light microscopy requires an amplification step with a silver physical developer. Silver-intensified colloidal gold probes can advantageously be used for immunostaining of cryostat, paraffin and plastic sections. Moreover, permeabilized cultured cells and whole-mount preparations can also be stained with gold-silver techniques. Silver intensification does not affect reactivity of a number of tissue antigens, thus permitting double staining combinations with immunoperoxidase or immunofluorescence methods.

Severe hypertension in humans may lead to fibrinoid necroses of cerebral blood vessels with small hemorrhages and cystic necroses. Similar lesions have also been reported in the experimental model of stroke-prone spontaneously hypertensive rats (SHRSP). We examined the genesis and spreading pattern of the brain oedema in SHRSP. The extravasation of plasma proteins was visualized with the Evans-Blue or the immunoperoxidase method. Most commonly the leakage occurred in the grey matter of the cerebral cortex or basal ganglia. The spreading pattern followed that of vasogenic brain oedema with a local spread in the grey matter and an extensive one in the white matter. In addition, we detected a novel pathway upwards along the perivascular spaces of the penetrating vessels as well as laterally in the subpial zone. This route is likely to serve also as a drainage channel for the oedema into the cerebrospinal fluid in the subarachnoidal space. Transfer of the extravasated proteins from the white matter to the ventricles was also observed, confirming that this previously described pathway for the resolution of oedema fluid exists in the SHRSP model of vasogenic brain oedema.

The differential mechanisms reducing androgen secretion by LHRH agonists are discussed with relevance to clinical therapy. LH secretion can be desensitised by exposure to agonists using high doses, frequent injections or sustained release/constant infusion. The desensitized pituitary is refractory to hypothalamic stimulation. Pituitary receptor suppression is associated with depletion of pituitary gonadotrophin content, and a decline of LH and FSH secretion to a basal rate. Recovery of LH responsiveness to endogenous LHRH stimulation requires restitution of gonadotrophin content (about 7 days in rats). After long-term infusions in normal men, testosterone secretion recovers within 7-10 days. The binding capacity of testicular LH/hCG receptors is reduced in rats after supraphysiological gonadotrophin stimulation, by agonists or directly by hCG, concomitantly the steroidogenic capacity of the testis in vitro is impaired. Qualitative changes in androgen biosynthesis are a marked fall in testosterone production and dose-dependent enhancement of progesterone production. After 12 months of buserelin injections, the changes in hCG-stimulated rat testes are an increased ratio of progesterone/17-OH-progesterone (inhibition of 17-hydroxylase), a reduced capacity for secretion of androstenedione and testosterone (block of 17,20-desmolase), and increased 5 alpha-pregnane-3,20-dione (this steroid inhibits the 17,20-desmolase, similarly to progesterone). After treatment, Leydig cell function recovers completely. Leydig cell hyperplasia is observed as a result of the steroidogenic changes. These findings in rats have not been observed in dogs, monkeys or in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological and pharmacological evidence is summarized for the existence of an inhibitory receptor system operated by glycine and another two separate systems operated by gamma-aminobutyric acid (GABA) through GABA-A and GABA-B receptors, respectively. Claims for subclasses of GABA-A receptor are critically reviewed and found not-proven. A quantitative pharmacological profile of the GABA-A receptor and associated regulatory sites for picrotoxin, barbiturates and benzodiazepines on the dorsal funiculus of the rat cuneate nucleus is described. When compared with this profile and the pharmacological properties of the glycine receptor complex, the effects of taurine cannot be entirely explained by actions on these two receptor systems.

Mononuclear phagocytes, a specialized cell lineage comprising bone-marrow precursors, blood monocytes and tissue macrophages, can interact with blood coagulation mechanisms with resulting thrombus formation or extravascular fibrin accumulation. Such procoagulant activity is usually activation dependent and requires interaction of the cells with immune or nonimmune stimuli. In the former case (e.g., alloantigens, soluble protein antigens) collaboration of mononuclear phagocytes with T lymphocytes is necessary and is mediated by cell-to-cell contact or lymphokines. Prototype of a direct acting stimulus is bacterial lipopolysaccharide. Mononuclear phagocyte procoagulant activity is expressed in the form of cell membrane-bound or released factors which display molecular heterogeneity. They include the initiator of the extrinsic clotting pathway, tissue factor, known clotting proteases such as factors V and VII, and novel proteolytic enzymes including prothrombinase and a factor X activator. Mononuclear phagocyte procoagulants are pathogenetically involved in generalized disorders with intravascular coagulation and thromboembolic phenomena. These disorders, exemplified by the Shwartzman reaction and possibly by paraneoplastic thromboembolism, are initiated by blood monocytes. Extravascular fibrin deposition can be initiated by tissue-infiltrating monocytes and macrophages in disease states such as acute renal allograft failure and solid tumours.

The effect of cardiopulmonary bypass (CPB) using high dose fentanyl anaesthesia on the concentrations of plasma arginine vasopressin (pAVP), serum electrolytes and osmolality was studied in 12 patients by repeated sampling up to 4th postoperative day. These values were also followed in another 20 patients for the first postoperative day. Fentanyl abolished the pAVP response often seen in major operations but not that produced by CBP. The pAVP concentration 4.8 +/- 0.8 pg/ml immediately after sternotomy increased to 27.2 +/- 1.5 pg/ml (P less than 0.001) after 5-10 minutes on CPB. By the 4th postoperative day the pAVP levels had reached normal values. The main reason for the elevated pAVP concentrations seems to be the onset of CPB, which provokes a fall in mean arterial pressure leading to pAVP release.

The intermediate and the neural lobe of the pituitary gland are innervated by two, virtually independent, groups of dopaminergic neurons which, until recently, were considered as a uniform system and referred to as the "tubero-hypophyseal dopamine system". Some aspects of the separate physiological functions of these neurons in the intermediate and in the neural lobe, of their microanatomy and biochemistry as well as of dopamine release from their terminals are discussed in this review.

Important progress has been recently made on the identification, physico-chemical properties, purification and production by recombinant technology of a series of immunoregulatory mediators, including interferons (IFNs). It is now possible to appreciate which part play IFNs in the regulation and activation of monocyte-macrophage (MO) functions. The present review discusses old concepts, such as Macrophage-Activating Factor (MAF) activity, at the light of recent data on the effects of IFN alpha, beta and gamma on four main immunological properties of MO, namely intracellular killing of microorganisms, non specific lysis of tumor cells, antigen presentation and secretion of soluble immunoregulatories molecules such as interleukin 1. All three IFN species enhance such functions, whereas enhancement of membrane class II major histocompatibility complex antigens is a unique property of IFN gamma. The role of IFNs, especially IFN gamma, as major MAF in vitro and in vivo is discussed.

The magnesium (Mg) content of human cancellous bone was studied in relation to its elemental composition and mineral density. The material was collected from 138 cadavers consisting men and women of different ages. Duplicate specimens from anterior iliac crest (one macerated and one fixed with alcohol) were obtained from individuals who had died suddenly or whose deaths were due to chronic immobilizing diseases. The cation concentrations were analyzed with an atomic absorption spectrophotometer, fluoride with the ion specific electrode, from macerated samples. The samples fixed in alcohol were used for determination of the mineral density with gamma rat attenuation. The mean Mg concentration (+/- SD) was 2.84 +/- 0.29 mg/g in the samples obtained from individuals who had died suddenly with no correlation with age. In the group with chronic diseases the mean Mg levels decreased slightly with increasing age. There was a significant, positive correlation between the Mg and Ca concentrations. In the linear regression analysis 16.4% of the variance of Mg concentration was accounted for by Ca. This relationship was more evident in men than in women. Only the postmenopausal women suffering from chronic diseases and having bone loss showed correlation between the bone Mg and Ca contents. The Mg/Ca ratio in men was quite constant and did not change significantly with age. In women the Mg/Ca ratio versus age showed no statistically significant relationship. The correlation between Mg and other elements was weak. The weak relationships between F and Zn to Mg clearly have no significant effect on the contents of these elements in bone.