Quantitation of urinary methylmalonic acid by gas chromatography mass spectrometry and its clinical applications

Urine methylmalonic acid (MMA) concentrations were detected in 79 Chinese patients by gas chromatography mass spectrometry (GC/MS), using a selected ion monitoring program. 10 of the 79 patients were found to have cobalamin deficiency. Their urine MMA amounts were all elevated with a mean value 1376 ng/microliter (11.66 mmol/l), ranging from 40.46 to 3900 ng/microliter (0.34-33.05 mmol/l). The remaining 69 cases were found to be unrelated to cobalamin deficiency. Their mean urine MMA was 3.62 ng/microliter (30.0 mumol/l), ranging from 0-17.47 ng/microliter (0-148.0 mumol/l). In this study, we found that urine MMA detected by GC/MS was a simple, rapid, convenient, specific and sensitive method for the diagnosis of cobalamin deficiency. The urine MMA concentrations in cases not due to cobalamin deficiency would not exceed 20 ng/microliter (169.5 mumol/l), whereas in cobalamin deficiency the urine MMA levels always exceeded 20 ng/microliter, or were even much higher. No overlapping of the results of urine MMA between these 2 groups of patients could be seen in our study. Detection of urine MMA is useful in the demonstration or exclusion of cobalamin deficiency in any suspect patients.

Migration as a demographic response: the age differentials

"This study uses the theory of demographic response as the background against which regional human migration is examined as a response to selected environmental conditions for the 1,056 counties in the North Central Region [of the United States]. Specifically, this study addresses two migration-related questions concerning county populations in the North Central Region: (1) What are the socioeconomic, demographic, and ecological factors to which county populations respond in adjusting their migration behavior? (2) Do socially important age cohorts respond to these factors differently or in a similar manner?" Factors affecting migration are employment status, income levels, educational status, ethnic group, residence location, marital status, home ownership, and age. Data are from the U.S. Census Bureau for the period 1965-1970.

Thy-1: a hydrophobic transmembrane segment at the carboxyl terminus

Thy-1 is a membrane glycoprotein distributed throughout mammalian species and expressed on brain tissue and various cells of the hematopoietic lineage. The nucleotide sequences of rat and mouse Thy-1 genes revealed a similar gene organization and the existence of an extra 31 amino acid segment at the carboxyl terminus not described previously. These extra amino acids, highly conserved in both species, include a 20 amino acid hydrophobic segment at the carboxyl terminus, which may be responsible for integration of Thy-1 within the plasma membrane.

Reduction of sera requirements in amniotic fluid cell culture

Reduction in serum requirement for culture of primary human amniotic fluid cells can be achieved by the addition of 10 growth-promoting factors to the nutrient medium. This supplemented medium preserves cell types normally found in amniotic fluid cell cultures supplemented with 20-30 per cent fetal bovine serum. The volume of amniotic fluid required to initiate culture can be as little as 1 ml. Amniotic fluid samples contaminated with red blood cells with no visible clot also grow well in the low serum medium. Cell-free amniotic fluid combined with equal parts of supplemented medium is useful in initiating cell culture.

The human T lymphocyte receptor complex for antigen and MHC

Recent studies using cloned antigen specific T lymphocytes and monoclonal antibodies directed at their various surface glycoprotein components have led to identification of the human T cell antigen receptor as a surface complex comprised of a clonotypic 90 KD Ti heterodimer and the in-variant 20 and 25 KD T3 molecules. Approximately 30,000-40,000 Ti and T3 molecules exist on the surface of human T lymphocytes. These glycoproteins are acquired and expressed during late thymic ontogeny, thus providing the structural basis for immunologic competence. The alpha and beta subunits of Ti bear no precursor-product relationship to one another and are encoded by separate germline V, D, J and C segments which rearrange during intrathymic differentiation to form an active gene set. Triggering of the T3-Ti receptor complex induces a rapid increase in free cytoplasmic Ca2+ and gives rise to specific antigen-induced proliferation through an autocrine pathway involving endogenous IL-2 production, release, and subsequent binding to IL-2 receptors. The implications of these findings for understanding of human T cell growth and its regulation in disease states are discussed.

Isolation and characterization of mouse Thy-1 genomic clones

The mouse Thy-1.2 gene was isolated from a C57Bl/6 cosmid library and its nucleotide sequence was determined from an 8-kilobase-long EcoRI fragment. The predicted amino acid sequence indicates that the mouse Thy-1 molecule contains a 19 amino acid leader peptide and the 112 amino acids reported previously from protein sequence analysis, plus 31 extra amino acids at the carboxyl terminus. These 31 amino acids contain a stretch of 20 amino acids, at positions 124-143, which is highly hydrophobic. RNA transfer blot analysis of RNA from mouse tissues indicates that the sequence coding for these 31 amino acids is present on poly(A)-containing RNA of brain and thymus tissues. This hydrophobic segment very likely provides the basis for integration of Thy-1 within the plasma membrane. The entire coding sequence of Thy-1 is distributed among three exons, encoding amino acid residues -19 to 8, -7 to 106, and 107 to 143, respectively. Comparison of the mouse and rat Thy-1 genes shows that both have a similar gene organization and encode a highly conserved transmembrane segment.

A hydrophobic transmembrane segment at the carboxyl terminus of thy-1

The mode of integration of the glycoprotein thy-1 within the cell membrane has been controversial due to an apparent lack of a transmembrane hydrophobic segment. Rat and mouse complementary DNA and genomic clones encoding the thy-1 molecule have been isolated and sequenced. These studies have enabled us to determine the intron-exon organization of the thy-1 gene. Furthermore, they have revealed the existence of a sequence which would encode an extra segment (31 amino acids) at the carboxyl terminus of the thy-1 molecule. These extra amino acids include a 20-amino acid hydrophobic segment which may be responsible for integration of thy-1 within the plasma membrane.

Structural organization of the rat thy-1 gene

Thy-1 is a differentiation marker expressed predominantly on thymocytes, T cells and brain tissue. Its presence on murine peripheral T cells but not B cells has long been used to distinguish between these two populations of lymphocytes. Although analogues of Thy-1 have been described in several mammalian species, its tissue distribution in different species varies widely, precluding its use as T-cell-specific marker. The Thy-1 molecule is a cell-surface glycoprotein of relative molecular mass 18,000, one-third of which represents carbohydrate; the protein moieties of the rat and murine Thy-1 molecules have been sequenced and found to consist of 111 and 112 amino acids, respectively. An unusual aspect of Thy-1 is the apparent absence of a hydrophobic segment comparable to that observed in other membrane glycoproteins which would allow integration of Thy-1 within the membrane lipid bilayer. This has prompted speculation that Thy-1 is anchored to the cell surface by some other hydrophobic component such as glycolipid. Here we report the structure of thy-1 complementary DNA and genomic clones and describe the exon-intron organization of the gene. More importantly, our data indicate that Thy-1 is initially synthesized as a molecule of 142 amino acids, 31 amino acids longer at the carboxyl end than the Thy-1 molecule isolated and characterized by Campbell et al. An extremely hydrophobic region of 20 amino acids lies within this 31-amino acid stretch and may represent the transmembrane segment responsible for anchoring Thy-1 to the cell membrane.

Biotin-labeled protein-A enzyme-linked immunosorbent assay for the detection of Japanese encephalitis antibody in sera from humans, swine and several animal species

Biotin-labeled protein-A was incorporated into enzyme-linked immunosorbent assay (ELISA) for seroepidemiological surveys of Japanese encephalitis (JE) virus infection in several vertebrates. The ELISA could detect the JE antibody in sera from man, rhesus monkey, swine, horse, dog, rabbit and mouse by the same reagent, but not in sera from cattle and pigeon. The titers of ELISA antibody were almost the same as those of 2-ME resistant HI antibody. Since non-specific reaction in ELISA was very low in the sera of swine and humans, the cut-off titer for the assay could be set at 1:5 for positive antibody.

Biotin-labeled antigen sandwich enzyme-linked immunosorbent assay (BLA-S-ELISA) for the detection of Japanese encephalitis antibody in human and a variety of animal sera

A biotin-labeled antigen (BLA) was adapted to a sandwich enzyme-linked immunosorbent assay (S-ELISA) for detection of Japanese encephalitis (JE) antibody in a variety of animal sera. JE antigen was fixed on the wells of a microplate and became bound to the specific antibody which could react with a peroxidase-labeled avidin conjugate and azino-di-(3-ethylbenzthiazolin sulfonic acid) (ABTS) as a substrate. The BLA-S-ELISA could simultaneously detect JE antibody in all hemagglutination inhibition (HI) positive sera from man, swine, monkey, horse, cattle, rabbit, rat, mouse and pigeon by using the same reagents under the same test conditions. The antibody titers obtained by BLA-S-ELISA in human and swine sera corresponded well with HI antibody titers. The sensitivity of BLA-S-ELISA appeared to be higher for IgM antibody than for IgG antibody. Since the non-specific reaction was extremely low in BLA-S-ELISA, the cut-off titer for the assay could be set as low as 1:2.5 of serum dilution for positive antibody.

Expression of the Thy-1 glycoprotein gene by DNA-mediated gene transfer

We isolated a gene encoding the Thy-1.2 glycoprotein from a recombinant library constructed from BALB/c mouse DNA. To evaluate the expression of this cloned gene in different genomic environments, we introduced it into cell lines derived from fibroblast, lymphoid, and neuronal tissues by DNA-mediated gene transfer. When integrated into the genome of mouse L cells, cell-surface Thy-1 can be detected with anti-Thy-1 monoclonal antibodies. These L-cell lines contain between two and four copies of the cloned Thy-1 gene stably integrated in the host genome. After subcloning into a plasmid vector containing the bacterial Eco-gpt gene as a selectable marker, the Thy-1 gene was introduced into the Thy-1-deficient mouse lymphoma AKR1 (Thy-1-d), and the rat neuronal cell line, B50. The resulting transformants also contain two to four copies of the cloned Thy-1 gene but express up to 50-fold more cell-surface Thy-1.2 than the L cell transformants. The expression of vastly differing amounts of cell-surface Thy-1 from similar numbers of genes suggests that the gene encoding this differentiation antigen is under tissue-specific regulation.

Partial phenotypic correction of human Lesch-Nyhan (hypoxanthine-guanine phosphoribosyltransferase-deficient) lymphoblasts with a transmissible retroviral vector

A human Lesch-Nyhan (hereditary, severe hypoxanthine-guanine phosphoribosyltransferase (HPR transferase) deficiency) B-lymphoblast line was infected with an amphotropic retroviral vector containing human HPR transferase cDNA under transcriptional control of viral long terminal repeat sequences. Of 17 clones isolated, 12 integration groups were defined by analysis of restriction enzyme digests of their genomic DNA with HPR transferase and viral long terminal repeat probes. These groups had HPR transferase activity restored to levels of 4 to 23% of normal values. Aberrant metabolic parameters associated with severe deficiency of HPR transferase activity, i.e. elevated rates of purine excretion, increased accumulation of hypoxanthine, elevated 5-phosphoribosyl-1-pyrophosphate contents, altered nucleoside triphosphate pools, resistance to toxic effects of 6-thioguanine, were partially to nearly completely corrected; the degree of correction generally corresponded to the degree of restoration of HPR transferase activity. The integration of the HPR transferase gene was found to be variably stable during 9 months of culture of the virally transformed lymphoblasts under nonselective conditions. The HPR transferase gene-infected lines reverted to resistance to 20 microM 6-thioguanine, i.e. severe HPR transferase deficiency, at frequencies of 10(-6) to in excess of 10(-5) per generation. The reversions were accompanied by either a loss or rearrangement of the integrated HPR transferase sequences or by retention of the sequences in an unaltered form.

The heavy chain of human B-cell alloantigen HLA-DS has a variable N-terminal region and a constant immunoglobulin-like region

The HLA-D region of the major histocompatibility complex (MHC) of man encodes polymorphic glycoproteins found predominantly on the cell surfaces of B cells and macrophages. These proteins mediate interactions, required for the induction of immune responses, among cells of the immune system and consequently are referred to as Ia (immune-response associated). Two families of Ia molecules, DR and DS (also known as DC), have been defined, the former analogous to the I-E (ref. 1) and the latter to the I-A molecules of the murine MHC. Both DR and DS molecules consist of two noncovalently associated polypeptide chains with molecular weights of 33,000 and 28,000, designated alpha and beta, respectively. The polymorphism of DR molecules is due to structural variation in the small subunit, DR beta, with the large subunit, DR alpha, being constant in structure. In contrast, both subunits DS alpha and DS beta are structurally variable when DS allotypes are compared. We have now isolated a cDNA clone from a DR7 cell line that contains the entire coding sequence for the DS alpha subunit and have compared its predicted amino acid sequence with that previously deduced from a DS alpha cDNA clone isolated from a DR4,w6 cell line. This comparison reveals that 10 of 11 amino acid differences are located within the alpha 1 (N-terminal) domain and that the alpha 2 or immunoglobulin-like domains are identical.

Thy-1 cDNA sequence suggests a novel regulatory mechanism

Thy-1 was originally defined in mice as a cell-surface alloantigen of thymus and brain with two allelic forms, Thy-1.1 and Thy-1.2 (ref. 1). Subsequently, the Thy-1.1 alloantigenic determinant was identified in rats. In both species, Thy-1 is present in large amounts on thymus and brain cells and in smaller quantities on fibroblasts, epidermal cells, mammary glands and immature skeletal muscle. In many of these tissues the level of Thy-1 expression changes dramatically during cell differentiation. The molecules expressing the Thy-1 antigenic determinant have been isolated from rat and mouse brain cells and have been shown to have a molecular weight of 17,500 (ref. 8). One-third of the Thy-1 molecule is carbohydrate and the remainder is a polypeptide of 111 amino acids whose sequence has been fully determined. We report here the isolation and characterization of a cDNA clone encoding the rat thymus Thy-1 antigen but find that the DNA sequence ends prematurely at a position corresponding to amino acid 103. It appears to be a complete transcript, however, as the last codon is followed directly by a poly(A) tract.

Further investigation on the hypothesis of meridian-cortex-viscera interrelationship

The hypothesis of Meridian-Cortex-Viscera Interrelationship maintains: 1. Meridian channel system is an independent system connected with the nerves to the cortex; 2. It acts through the nerves; 3. The nervous action is realized by humoral agents. This article gives preliminary-experimental supports for the above criteria.

Human amniotic fluid cells grown in a hormone-supplemented medium: suitability for prenatal diagnosis

A new supplemented medium has been developed to improve human amniotic fluid cell growth and to reduce the dependence on exogenously added serum. The medium consists of a mixture of Ham's F12 medium and Dulbecco's modified Eagle's medium supplemented with Hepes, antibiotics, and 10 growth-promoting factors at 4% fetal bovine serum. Good clonal growth is achieved consistently in 8--13 days and is associated with large numbers of metaphase cells. Primary clones may be analyzed directly, thereby reducing difficulty with interpretation of chromosomal mosaicism. This medium could also be used for cultivation of fetal solid tissues and peripheral blood cultures of lymphocytes.

Enhancement of human amniotic cell growth by Ficoll-Paque gradient fractionation

Ficoll-Paque isopycnic centrifugation was used as a preparative procedure for amniotic fluid (AF) cells prior to tissue culture. This technique serves to reduce contaminating erythrocytes and also enhances cell growth or mitotic indices. The technique described in this report yields three subfractions designated as a turbid interphase layer (F-2), a middle cell layer (F-3), and a bottom pellet (F-4). The middle cell layer (F-3) demonstrated better cell growth and higher mitotic index than any of the other fractions or control unfractionated amniotic fluid cells. The use of Ficoll-Paque isopycnic preparative centrifugation of amniotic fluid cells is a valuable adjunct in cell culture for cytogenetic analysis. This may be especially true when amniotic fluid contains large numbers of erythrocytes.

Neural origin of cells in amniotic fluid

Cells from the amniotic fluid of fetuses with open neural tube defects (NTDs) have several abnormal characteristics of potential diagnostic value. The cell number in a unit volume of fluid is 10 to 100 times the normal range of cell count. The majority of cells adhere to tissue culture dishes within 24 hours of inoculation, instead of the 4 or 5 days required by normal amniotic fluid cells. The rapidly adhering cells morphologically resemble glial cells. Their Coulter volume is about twice the average seen in normal amniotic fluid--derived cells. This larger number of oversized, rapidly adhering cells is likely due to the continuous accumulation of neural cells in the amniotic fluid. We have detected the presence of the glial protein S-100 and the absence of the neuronal protein 14-3-2 by using a specific immunofluorescence assay. We conclude that fetuses with NTDs shed large numbers of glialike cells into the amniotic fluid where their detection may have diagnostic importance.

Purification and some physicochemical properties of staphylococcal enterotoxin D

A method was developed for the isolation of staphylococcal enterotoxin D in highly purified form from cultures of Staphylococcus aureus strain 1151m. The method involves removal of the toxin from the culture supernatant fluid with the ion-exchange resin CG-50 followed by chromatography on carboxymethylcellulose (twice) and by gel filtration on Sephadex G-75 (twice). The purified toxin is homogeneous by polyacrylamide gel and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and double gel diffusion tests. It is a simple, colorless, antigenic protein with an isoelectric point of 7.4 as determined by isoelectric focusing. Its molecular weight was determined to be 27 300 +/- 700 by molecular sieve chromatography on Sephadex G-100 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its serological activity is stable over a wide range of pH values (1.2--10.7). The enterotoxin consists of 236 amino acid residues and contains no free sulfhydryl groups. End-group analysis showed serine to be the NH2-terminal amino acid and lysine to be the COOH-terminal amino acid.

Prognosis of clinically undiagnosed prostatic carcinoma and the influence of endocrine therapy

A 10-year series of 100 patients with clinically undiagnosed prostatic adenocarcinoma is presented. In 50 per cent of these patients the tumor was well differentiated and the survival was normal, while the remainder of the patients had moderately to poorly differentiated tumors and survival rates significantly less than normal. Of 8 deaths caused by cancer 7 were associated with less-than-well differentiated tumor. Patients who received endocrine therapy and died of causes other than cancer had a significantly shorter interval to death and a higher incidence of cardiovascular deaths than those who were untreated. While the majority of patients with incidental, clinically undiagnosed prostatic carcinoma is not at risk from the disease a minority exists who may benefit from radical therapy.

Effect of ammonium ions on the induction of nitrite reductase in Neurospora crassa

Results with strain am-la, a glutamate dehydrogenaseless mutant, showed that ammonium ions must first be metabolized in order to repress nitrite reductase in Neurospora.

Enzymatic and non-enzymatic reduction of nitrite by extracts of Neurospora crassa

Two activites causing nitrite disappearance are found in extracts of Neurospora; one, inducible by nitrate or nitrite and present only in nitrite-utilizing strains, catalyze the stoichiometric reduction of nitrite to ammonia; the other, present in all strains under all conditions, causes the disappearance of nitrite to something other than ammonia. The latter activity has a molecular weight of about 600 and may contain an oligopeptide, a metal, and an SH group(s). It has no known physiological function.