cis-Active Ras G2-like sequence implicated in the heterotropic activation of the deoxyadenosine kinase of Lactobacillus acidophilus R-26

Deoxyadenosine kinase (dAK) forms a heterodimer with either deoxyguanosine kinase (dGK) or deoxycytidine kinase (dCK), and is heterotropically activated 3-5 times by dGuo or dCyd. Expressed alone, dAK is inactive and exhibits no response to dGuo or dCyd; activity and heterotropic response are fully restored upon reassociation with dGK or dCK. However, turnover of independently expressed dGK or dCK is nearly maximal, being further activated only 50-100% upon reassociation with dAK. In neither case is the heterotropic activation due to ligand-induced heterodimer formation. A proline/alanine substitution within a dAK segment homologous to loop G2 of Ras proteins yielded a heterodimer with dAK permanently cis-activated 2-fold, with a corresponding reduction in heterotropic activation by dGuo. A chimeric dAK, with 25% of its C terminus substituted by the homologous sequence from dGK, was inactive alone, and its characteristics were unchanged in the reconstituted heterodimer. Superimposing the Pro/Ala substitution on this chimera also reduced heterotropic activation by half. Cross-linking the dimer by 1,5-difluoro-2,4-dinitrobenzene was inhibited by ATP, dATP, dGTP, and dAdo, suggesting the proximity of the active site(s) to the interface. These data suggest that dAK depends on dGK or dCK in a manner resembling the reliance of Ras upon GTPase activating protein.

Compromised blood-nerve barrier, astrogliosis, and myelin disruption in optic nerves during fatal murine cerebral malaria

We examined the optic nerve, as an analogous tissue to brain white matter, to assess possible relationships between changes in the blood-nerve barrier, axonal integrity, and astrocyte morphology in the central nervous system during fatal murine cerebral malaria (FMCM). In the FMCM model, namely, CBA mice infected with Plasmodium berghei ANKA, neurological symptoms begin around day 5 post-inoculation (p.i.) and mice become increasingly ill by day 7 p.i., at which time they lapse into coma and die. Using intravascular perfusion with horseradish peroxidase combined with light and electron microscopy, and GFAP immunohistochemistry, the optic nerves in malaria-infected mice were found to display i) breakdown of the blood-nerve barrier, detectable as early as day 3 p.i. (about 2 days before the onset of neurological symptoms) increasing to peak severity by day 7 p.i.; ii) monocytosis, vascular congestion, and monocyte adherence to the endothelium in the microvasculature during the later stages of the disease process; iii) an increased incidence of patchy axonal demyelination and degeneration, mostly associated with vascular changes and astrogliosis, beginning at day 5 p.i. and more evident by day 7 p.i.; and iv) an increased intensity of GFAP immunostaining, detectable from day 3 p.i. and peaking at day 7 p.i. These optic nerve changes were always seen in the infected individuals, though they varied in intensity. The temporal and anatomical coincidence between the compromised blood-nerve barrier, monocyte adherence to the vascular endothelium, astrocyte changes, neuronal degeneration, and demyelination in the optic nerve in FMCM suggests that these factors are mechanistically inter-related. These findings are consistent with the proposed immunopathological nature of FMCM and provide further evidence for the pivotal role of the CNS microvasculature in the disease process. This is the first investigation of involvement of the optic nerve in FMCM and the first demonstration, to our knowledge, of loss of axonal viability in this condition in any CNS tissue. The observed demyelination is consistent with reports by other workers on such changes in the brain in human cerebral malaria.

Mutations in TWIST, a basic helix-loop-helix transcription factor, in Saethre-Chotzen syndrome

Saethre-Chotzen syndrome is one of the most common autosomal dominant disorders of craniosynostosis in humans and is characterized by craniofacial and limb anomalies. The locus for Saethre-Chotzen syndrome maps to chromosome 7p21-p22. We have evaluated TWIST, a basic helix-loop-helix transcription factor, as a candidate gene for this condition because its expression pattern and mutant phenotypes in Drosophila and mouse are consistent with the Saethre-Chotzen phenotype. We mapped TWIST to human chromosome 7p21-p22 and mutational analysis reveals nonsense, missense, insertion and deletion mutations in patients. These mutations occur within the basic DNA binding, helix I and loop domains, or result in premature termination of the protein. Studies in Drosophila indicate that twist may affect the transcription of fibroblast growth factor receptors (FGFRs), another gene family implicated in human craniosynostosis. The emerging cascade of molecular components involved in craniofacial and limb development now includes TWIST, which may function as an upstream regulator of FGFRs.

Deoxycytidine kinase and deoxyguanosine kinase of Lactobacillus acidophilus R-26 are colinear products of a single gene

Three of the four deoxynucleoside kinases required for growth of Lactobacillus acidophilus R-26 exist as heterodimeric pairs specific for deoxyadenosine (dAK) and deoxycytidine (dCK) or dAK and deoxyguanosine (dGK). However, only two tandem genes, dak/dgk, are found, and are expressed only as dAK/dGK in transformed Escherichia coli. Sequencing peptides spanning 63% of the native dCK subunit revealed a sequence identical to that deduced from dgk (beginning MTVIVL...), except that dCK lacks residues 2 and 3 (dCK is M..IVL; dGK is .TVIVL). Also, mass spectrometry indicates that native dCK and dGK subunits are identical in mass adjusted for the first three residues. Furthermore, the native enzymes have identical isoelectric pH values, indicating an equal number of charged residues. To enable E. coli to express peptide having the native dCK sequence, codons 2 and 3 were deleted from the dgk portion of the tandem genes, resulting in expression of protein having the specificities and regulatory properties of native dAK/dCK, including heterotropic stimulation of dAK activity by deoxycytidine or dCTP (not deoxyguanosine or dGTP) and end-product inhibition of the respective activities by dATP and dCTP. Subcloning normal and mutant dgk yielded homodimeric dGK and dCK, respectively. The dCK homodimer strongly resembles human dCK, with a low K(m) for deoxycytidine, the ability to phosphorylate deoxyadenosine and deoxyguanosine at much higher K(m) values, and end-product inhibition by dCTP. Thus two distinct and specific enzymes evidently are derived from a single Lactobacillus gene. The mechanism by which this occurs in vivo has yet to be elucidated.

Correlation between enhanced vascular permeability, up-regulation of cellular adhesion molecules and monocyte adhesion to the endothelium in the retina during the development of fatal murine cerebral malaria

The relationships between increased vascular permeability to protein, monocyte adherence to the endothelium, and expression of the cell adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the central nervous system microvasculature were studied during the progression of fatal murine cerebral malaria. CBA mice were inoculated with Plasmodium berghei ANKA, and changes in the retinal microvasculature were examined on days 3, 5, and 7 postinoculation (p.i.). Evans blue dye and horseradish peroxidase (HRP) were administered intravenously to assess vascular permeability to macromolecules macroscopically and by light and electron microscopy. ICAM-1 and VCAM-1 expression were examined by immunohistochemistry. HRP leakage into the retinal parenchyma was seen macroscopically at a low level on day 3 p.i., increasing progressively at day 5 (the earliest time at which cerebral symptoms were observed) and day 7 (the day on which animals showed severe behavioral abnormalities and died). The inner retinal vascular plexus showed a slight increase in vascular permeability to intravenous Evans blue at day 3 p.i. and congestion, monocyte adherence to the endothelium, and increased vascular permeability to both Evans blue and HRP at day 7 p.i. Electron microscopic observations were consistent with these findings and also revealed disrupted light junctions and the coating of monocytes and endothelium with HRP at day 7 p.i. Immunohistochemical staining and densitometry showed a progressive increase from day 3 to day 7 p.i. in the densities of ICAM-1 and VCAM-1 on the venular endothelium of the inner retinal vascular plexus, with the appearance of adherent ICAM-1+ monocytes at the terminal stage of the disease. None of the pathological changes associated with the inner retinal plexus were seen at any stage in the outer retinal plexus. These results suggest the following sequence of events in the inner retinal vessels, particularly the venules, during the progression of fatal murine cerebral malaria: 1) a mild increase in vascular permeability at approximately day 3 p.i., 2) a progressive increase in endothelial expression of the cell adhesion molecules ICAM-1 and VCAM-1, commencing at approximately day 3 p.i., 3) monocyte adhesion to the endothelium starting at approximately day 5 p.i., and 4) frank disruption of endothelial integrity at the terminal stage (day 7 p.i.), leading to edema and hemorrhage. Similar changes in cerebral vessels may underlie the neurological complications of the disease.

[Relationship between wound healing and TNF, MDA and SOD contents in granulation tissues of rats in the first week]

An experimental model was used to determine the changes in TNF, MDA and SOD in granulation tissues during natural wound healing after skin excision on rats. Our results indicated that the changes in TNF and SOD exhibited a curve of V. The levels of TNF and SOD were lower on day 7 than day 3. The levels of MDA rose gradually, especially on day 7. A positive correlation was shown between TNF and MDA (at days 3, 5, 7), also between TNF and SOD (at day 3, 7). When the concentration of TNF was lower than 90 Pg/mg protein, the process of wound healing was best, while wound healing was hindered when the levels of SOD were low. The results suggest that in the process of wound repair there are influential changes in the contents of TNF, MDA and SOD. Lower levels of TNF and higher levels of SOD are apparently beneficial to wound healing after trauma.

Glial uptake of intracerebroventricularly injected D-serine in the rat brain: an immunocytochemical study

Recent studies have shown that free D-serine, an agonist for the N-methyl-D-aspartate receptor, is present in the forebrain of rats. In present study, we raised antibodies against D-serine and examined the distribution of both endogenous and intracerebroventricularly administered D-serine in the rat forebrain by an immunocytochemical method. D-Serine-like immunoreactive cells were found in glial cells in the brains of the rats injected with D-serine into the lateral ventricle. No immunoreactive cells were seen in the brains of untreated rats. The results suggest that glial cells may accumulate and catabolize D-serine to regulate the concentration of this neuroactive amino acid in the forebrain.

[Study of H(+)-Ca2+ exchange in cultured heart cells after hypoxia and reoxygenation]

Reoxygenation is more serious for hypoxic myocardial cells because of the subsequent calcium overload. The calcium overload is known due to augmentation of H(+)-Na+, Na(+)-Ca2+, exchange during pH paradox. But the present experiment showed that, when H(+)-Na+, Na(+)-Ca2+ exchange was inhibited, calcium could still enter myocardial cells after hypoxia or reoxygenation. Similar result was observed after using Na(+)-Free solution, suggesting that calcium entrance into the cell was unrelated to Na+ channel. It was further shown that calcium accumulation was related to pH gradient across the myocardial cell membrane, i.e., being increased with increase of H+ concentration in the cell. Therefore, it appears that, besides H(+)-Na+, Na(+)-Ca2+ exchange, H(+)-Ca2+ exchange is one of the reasons of calcium overload during intracellular pH paradox.

Xq-Yq interchange resulting in supernormal X-linked gene expression in severely retarded males with 46,XYq- karyotype

The critical importance of dosage compensation is underscored by a novel human syndrome ("XYXq syndrome") in which we have detected partial X disomy, demonstrated supernormal gene expression resulting from the absence of X inactivation, and correlated this overexpression with its phenotypic consequences. Studies of three unrelated boys with 46,XYq- karyotypes and anomalous phenotypes (severe mental retardation, generalized hypotonia and microcephaly) show the presence of a small portion of distal Xq on the long arm of the Y derivative. Cells from these boys exhibit twice-normal activity of glucose-6-phosphate dehydrogenase, a representative Xq28 gene product. In all three cases, the presence of Xq DNA on a truncated Y chromosome resulted from an aberrant Xq-Yq interchange occurring in the father's germline.

An immunohistochemical study of aspartate, glutamate, and taurine in rat kidney

Biochemical studies have revealed considerable amounts of free amino acids in the kidney. We examined the intrarenal distribution of three amino acids (aspartate, glutamate, and taurine) in the rat kidney with an immunoperoxidase method. In the renal cortex, all three amino acids were concentrated in the renal corpuscles and in the epithelia of the collecting tubules. Immunostaining of the collecting tubules was more intense in the principal cells than in the intercalated cells. The distal convoluted tubules were also immunostained with aspartate- and glutamate- specific antibodies but not with the taurine-specific antibody. In the renal medulla, the immunoreactivity specific for aspartate and for glutamate was similar; it was weak in the thick portion of the loop of Henle and strong in the collecting tubules. Immunoreactivity specific for taurine was restricted to regions within the epithelia of the thin portion of the loop of Henle and the collecting tubules. The significance of the accumulated amino acids as osmoregulatory agents is discussed.

Biochemical and morphological alterations of macrophages and spleen cells produced by antitumor polysaccharide from Acanthopanax obovatus roots

Acanthopanax obovatus polysaccharide (AOPS) administrated intraperitoneally (i.p.) resulted in the augmentation of phagocytosis and the chemiluminescence in peritoneal macrophages of mice. Binding of the third component of complement (C3) cleavage products to the receptors on peritoneal macrophages was enhanced by AOPS. The C3 conversion in human serum was increased by AOPS in vitro treatment. When given i.p., AOPS led to the enhancement of spleen weight, spleen cell number, and plaque-forming cells. It was also found that after in vivo administration AOPS not only enhanced the synthesis of DNA and protein but also promoted the mitogenic responses of spleen cells. The morphological observation of spleens indicated that AOPS augmented the transformation from lymphocytes to plasma cells. AOPS inhibited the growth of mouse solid Sarcoma-180 and prolonged the survival time significantly. These results suggest that AOPS is an effective biological response modifier and its antitumor activity is related to its immunopotentiating effects.

Isolation of 1001 new markers from human chromosome 11, excluding the region of 11p13-p15.5, and their sublocalization by a new series of radiation-reduced somatic cell hybrids

The determination of the physical map of human chromosome 11 will require more clones than are currently available. We have isolated an additional 1001 new markers in a bacteriophage vector from a somatic cell hybrid cell line that contains most of chromosome 11, except the middle of the short arm. These markers were localized to five different regions, 11p15-pter, 11p12-cen, 11q11-q14, 11q14-q23, and 11q23-qter, by a panel of previously characterized somatic cell hybrids. The region 11q11-14 harbors genes that have been shown to be important in breast cancer, B-cell lymphomas, centrocytic lymphomas, asthma, and multiple endocrine neoplasia, type 1 (MEN1). To determine the positions of the recombinant clones located there, we developed a new series of radiation-reduced somatic cell hybrids. These hybrids, together with those previously characterized, allowed us to map the 11q11-q14 markers into 11 separate segregation groups.

Growth hormone secretion in Alzheimer's disease: 24-hour profile of basal levels and response to stimulation and suppression studies

The 24-h growth hormone secretory pattern and GH response to growth hormone releasing hormone, the alpha 2-adrenoceptor agonist clonidine and the somatostatin-analogue SMS 201-995 were evaluated in 9 patients with Alzheimer's disease and 9 age- and body body-matched control subjects. The secretory profile did not differentiate between patients and controls. Both secreted the largest amount of GH during the early nighthours between 22.00-02.00, whereas the majority of daytime GH levels were below the assay's detection limit (0.4 ng/ml). No difference was found in GH response to GHRH between patients and controls. All subjects showed significantly enhanced GH secretion after GHRH. Dividing the patients into two groups according to age-of-onset (less than 60 years greater than), there was a trend toward larger GH responses to GHRH for the early-onset group. No other parameter differentiated the groups. GH levels after clonidine were blunted in all subjects but one AD patient, probably due to an age-dependent attenuation frequently observed in subjects over 45 years of age. Finally, the administration of the somatostatin-analogue did not render conclusive results, since spontaneous decline of GH concentration was already beginning 2 hours before the drug was given and continued steadily throughout the observation period. In conclusion, patients with only mild to moderate degree of Alzheimer's disease have no prominent changes in GH regulation.

Anionic sites in diabetic basement membranes and their possible role in diffusion barrier abnormalities in the BB-rat

Basement membrane anionic sites, thought to be responsible for charge selective permeability barriers, were investigated in retinal, endoneurial, and muscle capillary basement membranes and in Bruch's membrane of diabetic, and age- and sex-matched non-diabetic BB-rats using an ultrastructural quantitative histochemical technique. Six months of diabetes was associated with significant basement membrane thickening which was linearly related to a decrease in anionic site density suggesting a relative loss of proteoglycans. Calculation of anionic sites per unit length of basement membrane, reflecting their absolute number, revealed a significant loss in basement membrane, constituting part of normal blood-tissue barrier systems such as retinal and endoneurial capillary basement membranes, and the basement membrane of the retinal pigment epithelium. The absolute number of anionic sites in normally permeable microvessels, such as those of muscle and choriocapillaries, was unaltered by diabetes. We conclude that this specific loss of anionic sites in basement membranes of tissues affected by chronic diabetic complications may in part be responsible for permeability abnormalities seen in these tissues.

Synchronization of hormonal time series: analytical approaches

Comparison of the patterns of episodic secretion of two or more hormones measured simultaneously often suggests that peak levels tend to occur at around the same time. This visual impression can be misleading, however, as some peaks will occur simultaneously due to chance alone. Traditional cross-correlation methods are suitable for evaluating linkages among circadian and other smoothly varying rhythms, but are less well suited to correlating ultradian peaks. This paper proposes a method which entails identifying peaks of hormone secretion as discrete events in several different series, and counting the frequency of simultaneous and near-simultaneous peaks in temporal 'windows' of increasing width. The expected rates of random coincidences can be assessed by a variety of methods, including simulations and probability calculations. The method described utilizes simple techniques which make few assumptions about the character or stationarity of the series, comparing coincidence rates in the appropriately paired series with those in which a series in one subject is deliberately 'mismatched' with that of another subject. Using this approach, a significant excess of simultaneous peaks of luteinizing hormone (LH) and prolactin was found in normal subjects as compared with mismatched series (17% versus 6%; p less than 0.05). Hypogonadotrophic men treated with pulsatile gonadotrophin-releasing hormone (GnRH) have an even higher coincidence rate (26%). By contrast, the rate of coincidence between pulses of LH and cortisol is not significantly greater than that which would be expected due to chance.

Reduced number of anionic sites is associated with glomerular basement membrane thickening in the diabetic BB-rat

Glomerular basement membranes of diabetic and age- and sex-matched non-diabetic BB rats were studied morphometrically and ultrastructurally using a quantitative histochemical technique employing the cationic dye cuprolinic blue. Six months of diabetes resulted in a significant reduction in the density of anionic sites associated with increased thickness of the glomerular basement membrane. These findings suggest that the loss of anionic sites may be an important mechanism in the genesis of glomerular basement membrane dysfunction in diabetes.

[The effect of ginseng stem, leaf and rhizoma saponins on the formation of lipid peroxides in rats of various ages]

The effect of saponins isolated from the stem, leaf and rhizoma of panax ginseng on the formation of lipid peroxides in aged (30, 24 and 20 months) and middle-aged (14 months) wistar rats was studied with both in vivo and in vitro methods. The results showed: The formation of lipid peroxides increased with age in rats and mice: the two saponins of ginseng stem, leaf and rhizoma can obviously inhibit the lipid peroxidation in the serum (plasma) and liver homogenate of aged and middle-aged rats (p less than 0.05 and less than 0.001). The same effect was also shown in the aged LACA mouse (18 months) experiment.

Methods for assessing the linkage between pulsatile hormone profiles

Although the different anterior pituitary hormones are generally considered to be regulated independently, examination of their patterns in blood suggests that pulsatile secretion of several of these hormones may be synchronized. Traditional methods of cross-correlation analysis may not be adequate for quantifying this linkage. Since some simultaneity may arise by chance, expected rates of random coincidences must also be estimated to determine if apparent concordance rates significantly exceed those due to chance. A method of estimating linkage by counting simultaneous and near-simultaneous events within temporal 'windows' of varying width is proposed and tested against 11 series of luteinizing hormone (LH) and prolactin measurements from normal men. Rates of concordance in series drawn from different subjects rather than the same subject, or series scrambled in time, do not contain meaningful simultaneous events and so can be used to estimate the rate of random synchrony. By these standards, a clear excess of concordant prolactin and luteinizing hormone (LH) peaks was observed in normal men, suggesting significant physiological synchrony between these pulses of secretion. This method can be applied to a variety of hormonal systems.

Primate evolution of a dispersed human repetitive DNA sequence

A dispersed middle repetitive DNA sequence isolated originally from human chromosome 12 did not show homology with rodent DNA under standard conditions of Southern DNA blot analysis. The evolutionary relationship of this human repetitive DNA to that of other primates was investigated using three hybridization methods: DNA dot blot, Southern DNA blot analysis, and chromosome in situ hybridization. Homology with the human repetitive DNA was found throughout the suborder Anthropoidea, in fourteen ape and New and Old World monkey species. In addition, the human pattern of hybridization to noncentromeric regions of all chromosomes was seen. No hybridization by any of the three techniques was found in five species of the suborder Prosimii. The phenomenon of marked differences in sequence homology and copy number of dispersed repetitive DNA from closely related species has been observed in protozoans (Plasmodia), Drosophila, sea urchins, mice and the great apes (Hominoidea). We report here a similar phenomenon that may have occurred at an early stage in primate evolution.