Coexpression of cytokeratin and vimentin in Rathke's cysts of the human pituitary gland

Summary Immunohistochemistry with monoclonal and polyclonal antibodies revealed the presence of cytokeratins in epithelial cells of Rathke's cysts in the pars intermedia of the human pituitary gland. With monoclonal antibodies specific for individual cytokeratins, the expression of CK 18, CK 8, CK 7, and CK 19 could be shown in these cells. Within the hypophysis, CK 19 and CK 7 were restricted to Rathke's cysts and a few epithelial cell clusters in the pars tuberalis, whereas other cytokeratins were also present in endocrine cells of the pars distalis. Furthermore, vimentin and, focally, glial fibrillary acidic protein (GFAP) were detected in the cystic epithelia. By double labelling, coexpression of cytokeratin and vimentin, GFAP and cytokeratin, and GFAP and vimentin could be demonstrated. Compiled data of all known cases of coexpression of cytokeratin and vimentin in normal cells reveal physiological correlations and suggest a functional significance of this rare type of coexpression of intermediate filament proteins.     

Basement-membrane components associated with the extracellular matrix of the lymph node

Summary Lymph nodes contain an extensive array of extracellular matrix fibers frequently referred to as reticular fibers because of their reticular pattern and positive reaction with silver stains. These fibers are known to contain primarily type-III collagen. In the present study, frozen and plastic-embedded sections of mouse and human lymph nodes were subjected to immunostaining with a panel of monospecific antibodies directed against type-IV collagen, type-III collagen, laminin, entactin, and heparan sulfate proteoglycan. Immunofluorescent staining revealed that, in addition to being uniformly stained with antibodies to type-III collagen, these fibers also stained positively with antibodies to type-IV collagen and to other basement-membrane-specific components. Furthermore, the basement-membrane-specific antibodies stained the outer surface of individual fibers. These same type-III collagen-rich fibers were distinct from blood vascular basement membranes since they did not react with antibodies to factor VIII-related antigen, an endothelial-cell-specific marker. The role of these basement-membrane-specific components associated with the reticular fibers of lymphoid tissue is unknown. However, it is possible that the ligands promote attachment of reticular fibroblasts as well as macrophages and lymphocytes to the extracellular matrix fibers.     

Seasonal changes in circadian rhythms of body temperatures in humans living in a dry tropical climate

Seven volunteers (3 females and 4 males; 3 Caucasians and 4 Africans) participated in two 24 h sessions during the cool dry (CD) and the hot dry (HD) seasons of the sahelian tropical climate. Body temperatures were taken on portable cassette recorders for 24 h. Rectal (Tre) and mean skin (Tsk) temperatures decreased in the HD compared to the CD conditions, meeting one of the criteria for adaptation to heat. No ethnic differences in thermal responses were found. Males and females differed in their body temperature rhythms and in their reactions to heat. Body temperatures were higher in females than in males. Males reacted to heat with a decrease in Tre, without change in the Tre-Tsk gradient. Females showed a decrease in both Tre and Tsk, more marked for Tsk, with an increase in the Tre-Tsk gradient. It was concluded that males showed seasonal acclimatization to heat via a decrease in metabolism confirmed by a decrease in plasma levels of thyroid stimulating hormone (TSH) in the HD condition. Females showed a mixed metabolic and thermolytic type of acclimatization, with an absence of variation in plasma TSH levels. In conclusion, the steady rise in temperature between the CD and HD conditions was sufficient to trigger an acclimatization to heat similar in Caucasian and African subjects, although exposure to the external climate differed widely.     

Characteristics of human milk glutathione peroxidase

Human milk glutathione peroxidase (GPx) was purified 4500-fold using acetone precipitation and purification by repetitive ion-exchange and gel filtration chromatography with an overall yield of 34%. Homogeneity was established by gel electrophoresis. Using gel filtration, the molecular weight (mol wt) of the enzyme was estimated to be 92 kdalton (kD). The monomeric molecular weight was estimated to b 23 kD from polyacrylamide gel electrophoresis, indicating that the native enzyme consists of four identical subunits. The molecular weight of each subunit was supported by amino acid analysis. Selenium (Se) content of the purified enzyme was 0.31%, in a stoichiometry of 3.7 g-atoms/mol. Data from these studies reveal that GPx provided approximately 22% of total milk Se, but only 0.025% of the total protein.     

Ca- and Mg-dependent association of phosphorylase kinase with human erythrocyte membranes

The interaction of rabbit muscle phosphorylase kinase (EC 2.7.1.38) with human erythrocyte membranes was investigated. It was found that at pH 7.0 the kinase binds to the inner face of the erythrocyte membrane (inside-out vesicles) and that this binding is Ca²⁺- and Mg²⁺-dependent. The sharpest increase in the binding reaction occurs at concentrations between 70 and 550 nM free Ca²⁺. Erythrocyte ghost or right-side out erythrocyte vesicles showed a significantly lower capacity to interact with phosphorylase kinase. Autophosphorylated phosphorylase kinase shows a similar Ca²⁺-dependent binding profile, while trypsin activation of the kinase and calmodulin decrease the original binding capacity by about 50%. Heparin (200 μg/ml) and high ionic strength (50 mM NaCl) almost completely blocks enzyme-membrane interaction; glycogen does not affect the interaction.     

The effects of guanine and cytosine variation on dinucleotide frequency and amino acid composition in the human genome

Summary One hundred twelve human DNA sequences were analyzed with respect to dinucleotide frequency and amino acid composition. The variation in guanine and cytosine (G+C) content revealed: (1) at 2–3 and 3-1 doublet positions CG discrimination is attenuated at high G+C, but TA disfavor is enhanced, and (2) several amino acids are subject to G+C change. These findings have been reported in part for collections of sequences from various species. The present study confirms that in a single organism-the human-the G+C effects do exist. Aspects of the argument that connects G+C with protein thermal stability are also discussed.     

[3H]Imipramine Binding of Protein Nature in Human Platelets: Inhibition by 5-Hydroxytryptamine and 5-Hydroxytryptamine Uptake Inhibitors

Abstract: The nature of [³H]imipramine binding to human platelets was investigated. Desipramine and 5-hydroxytryptamine (5-HT) displaced the same amount of binding and the binding was sensitive to protease treatment. The nature of pharmacological inhibition of [³H]imipramine binding was investigated in saturation experiments. Increases in K d without changes in B _max were noted with the addition of 5-HT, desipramine, norzimeldine, or 5-methoxytryptoline. Reductions in B _max without alterations in K _D were obtained when citalopram or clomipramine was added. It is concluded that the [³H]imipramine binding site in human platelets is of protein nature and that this binding site contains the substrate recognition site for 5-HT uptake. In addition, [³H]imipramine and other 5-HT uptake inhibitors have bonds to other parts of the 5-HT uptake carrier or to the surrounding lipid membrane. This additional binding outside the substrate recognition site is not one single site but most likely represents sites that are specific for the chemical structure of each uptake inhibitor, respectively.     

Autoradiographic Analysis of [3H]Imipramine Binding in the Human Brain Postmortem: Effects of Age and Alcohol

In vitro quantitative autoradiography of high-affinity [3H]imipramine binding sites was performed on 16 human brains postmortem. The densities of binding sites were highest in the hypothalamus. Next, in descending order, were the basal and lateral nuclei of the amygdala; substantia innominata; insular cortex; the central nucleus of the amygdala; the anterior nucleus of the thalamus; the head of the caudate nucleus; portions of the frontal, parietal, and temporal cortex; claustrum; the granular layer of the dentate gyrus; substantia nigra; the pyramidal layer of CA fields; globus pallidus; red nucleus; and white matter. Imipramine binding was found to increase with age in a region-specific manner. The presence of alcohol had a similar effect, which was most pronounced in the hippocampus. Sex and time from death to autopsy did not affect imipramine binding, in our sample.     

Structural Features of Human Monoamine Oxidase A Elucidated from cDNA and Peptide Sequences

Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states.     

The effects of traditional gathering on populations of the marine gastropod Strombus luhuanus linne 1758, in southern Papua New Guinea

Summary Little is known of the response of mollusc populations to predation by humans, particularly for tropical species. In this paper, we examine the effects of human predation on populations of the gastropod Strombus luhuanus in Bootless Inlet, Papua New Guinea, by documenting both the population biology of the shellfish and the shell-gathering practices of traditional and contemporary human groups. Strombus luhuanus occurs in local colonies and individuals of each sex from different colonies differed significantly in size. Sexual maturity is reached within two years after settlement, at which time the shell length stabilises at about 35–60 mm, and the shell lip thickens. There was also significant between-colony variation in density (8.35–23.39 individuals/m²), and colonies differed in the depth range of their distributions and the frequency of human collection visits. Traditional gatherers rarely collected individuals which were buried or subtidal. Contemporary collectors used different collecting methods, and gathered subtidal populations to a depth of 2.5 m. Both traditional and contemporary collectors gathered only individuals greater than 30 mm shell length, and in the contemporary sample the probability of being gathered increased significantly with shell length. This was due to size-dependent burying, which was greatest among young juveniles and least among adults. The traditional sample contained fewer shells in the largest size category (>45 mm) and more in the smallest (<40 mm), but this difference largely represents the pooling of shells from different collecting locations rather than widespread juvenisation of colonies due to exploitation. Stromb population densities at collected sites in PNG far exceeded those in comparable uncollected sites in northeastern Australia. We conclude that S. luhuanus displays high resilience to all gathering practices used to date, as a consequence of both its size-dependent burying and partly subtidal distribution, which provide refugia from human predation.