On two tests of fit for HLA data with no double blanks.

Stevens suggests a test of fit, based on Bernstein's estimators, of the Hardy-Weinberg law for the ABO system. Nam and Gart extend this test to the generalized ABO-like system and apply it to HLA data. When the recessive gene is rare, Huether and Murphy recall Haldane's point that its Bernstein's estimator is negatively biased and go on to suggest novel corrected versions of it. With the identification of more HLA antigens, it is not uncommon to find, in certain populations, that the sample data contain no double blanks; that is, every individual reacts to at least one antigen for a given locus. Gart and Nam give a simple score test of a zero true recessive-gene frequency for such situations. Here we examine the extended test of Stevens as a test of this hypothesis. We find that it is fully efficient for two codominant alleles but that when the number exceeds two its efficiency may be 50% or lower or as high as 100%, depending on the number of alleles and the pattern of gene frequencies. The tests are applied to a set of HLA data.     

Urinary gonadotropin fragment (UGF) measurements in the diagnosis and management of ovarian cancer

UGF is a small peptide present in the urines and tissues of patients with gynecologic cancers. Published research (which, at present, mainly comes from our laboratory) on the general application of UGF as a tumor marker, and on its use in the diagnosis of ovarian cancer, is reviewed, and new studies on its use, alone and with CA125, in the management of patients with ovarian cancer, are presented. In 234 healthy women, 89 with benign disease, and 79 with ovarian cancer, UGF levels were above 3 fmol/ml (low cut-off) in 12 percent, 7 percent, and 82 percent, respectively, and above 8 fmol/ml (high cut-off) in 1.7 percent, less than 1.1 percent, and 59 percent, respectively. Similarly, 11 percent, 14 percent, and 70 percent, respectively, had CA125 levels above 35 U/ml (low cut-off), and less than 1.9 percent, 1.2 percent, and 49 percent had levels above a 200 U/ml (high cut-off). Ideally, the higher UGF and CA125 cut-offs should be used for diagnostic applications, like differentiation of a benign from a malignant pelvic mass (false-positive rate: UGF, less than 1.1 percent; CA125, 1.2 percent), but raising the cut-offs diminishes sensitivities for malignancy (UGF, 59 percent; CA125, 49 percent). The populations detected by the two markers only partially overlap, however, so that, together, UGF or CA125 can identify 75 percent of malignant pelvic masses. Levels of UGF (cut-off, greater than 3 fmol/ml) and CA125 (35 U/ml) were also monitored in 30 women undergoing therapy for ovarian cancer. Clinical observations were reflected at each clinic visit by UGF alone in 67 percent, by CA125 alone in 57 percent, and by UGF and CA125 together in 87 percent of cases. While separately UGF and CA125 levels predicted 71 percent and 57 percent, together they forecast 86 percent of recurrent cancers prior to clinical manifestations. UGF and CA125 should be used together in the detection and management of ovarian cancers.     

Effect of water activity on enzymatic synthesis of cephalexin

Summary In enzymatic synthesis of cephalexin (CEX) from 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D--phenylglycine methyl ester (PGM) using an acylase fromXanthomonas citri, it was found that the synthetic activity and conversion yield were enhanced markedly by depressing the water activity (a _w ) of reaction system. This enhancement was probably resulted from the change of thermodynamic equilibrium and maximized at a range ofa _w from 0.96 to 0.97.     

Citric acid production by Aspergillus niger immobilized on polyurethane foam

Summary Citric acid was produced using Aspergillus niger immobilized on polyurethane foam in a bubble column reactor. Most of the adsorbed cells remained on the support and, as a result, high oxygen tension was maintained during the reactor operation. However, uncontrolled growth of the pellets made continuous reactor operation difficult. The citric acid productivity obtained from 15 vol.% foam particles containing immobilized cells was 0.135 g/l per hour. This productivity of immobilized cells was almost the same as that of free cells. The oxygen level dropped to half saturation in 5 days in the immobilized cell culture in contrast to 2 days in the free cell culture.     

Dual translational initiation sites control function of the lambda S gene.

Lysis gene S of phage lambda has a 107 codon reading frame beginning with the codons Met1-Lys2-Met3. Genetic data have suggested that translational initiation occurs at both Met1 and Met3, generating two polypeptides, S107 and S105 respectively. We have proposed a model in which the proper scheduling of lysis depends on the partition of translational initiations between the two start codons. Here, using in vitro methods, we show that two stem-loop structures, one immediately upstream of the reading frame and a second approximately 10 codons within the gene, control the partitioning event. Utilizing primer-extension inhibition or 'toeprinting', we show that the two S start codons are served by two adjacent Shine-Dalgarno sequences. Moreover, the timing of lysis supported by the wild-type and a number of mutant alleles in vivo can be correlated with the ratio of ternary complex formation over Met1 and Met3 in vitro. Thus the regulation of the S gene is unique in that the products of two adjacent in-frame initiation events have opposing function.     

Effects of phorbol ester and teleocidin on Ca2+-induced fusion of liposomes

The effects of different types of lipid membrane defects on Ca2+-induced fusion of liposomes containing phosphatidylserine (PS) were investigated using fluorescent probes. Teleocidin enhanced the fusion of phospholipid vesicles in an assay system using terbium/dipicolinic acid during mixing of internal aqueous phases of vesicles upon fusion. 12-O-Tetradecanoylphorbol-13-acetate (TPA) suppressed the fusion. This latter phenomenon was also observed by measuring the excitation energy transfer. The promotion of membrane fusion by teleocidin was ascribed to dehydration of the membrane surface, the suppressive effect of TPA to desorption of Ca2+ from the membrane surface. Thus, Ca2+-induced fusion of PS vesicles was shown to be sensitive to defects of the membrane surface, but insensitive to defects of the hydrophobic core of the lipid membrane.     

A reevaluation of the amino acid sequence of human follitropin beta-subunit

A collaborative study from two laboratories has been undertaken to re-evaluate the human follitropin -subunit sequence (hFSH), since areas of uncertainty remain in the wake of two earlier reports. The first report was by Shome and Parlow (1974). The second, by Saxena and Rathnam (1976), proposed revisions for sequence not definitively placed in the first study, as well as some differences in other placements. We have re-examined the sequence of the hFSH with more recent methodology. This has led to revision of certain areas of the sequence and resolution of differences between the two earlier proposals. Specifically, an-Ile-Ser- is established at 21–22, Asp at 41, Arg at 44, Lys at 46, and Glu at 111. These were areas of disagreement in the earlier proposals. A definitive placement of the residues around tryptophan-27 has now been obtained by three laboratories. C-terminal heterogeneity was observed with subunits ending at residue 107, 109, or 111. N-terminal heterogeneity has been observed in all preparations examined to date. A significant population of molecules with a proteolytic nick between residues 38–39 is noted. This is very likely an artifact of the collection and processing. The preparations examined in the present studies showed no evidence of residues 112–118 proposed by Saxena and Rathnam.     

Estimation of oxygen penetration depth in immobilized cells

Summary A simple method is proposed for calculating oxygen pentration depth in immobilized cells by assuming zero order kinetics in the presence of several external oxygen transport resistances. Calculations indicate that typical penetration depths of oxygen for immobilized microbial cells are in the range of 50–200 and those for immobilized or encapsulated animal and plant tissue culture are about 500–1000 . Based on calculations, oxygen transport in microencapsulation and microcarriers for tissue cultures are not transport-limited, but a slight limitation is expected for those in a hollow fiber reactor.Nomenclature a_s specific area of a support (cm) - Bi Biot number - dimensionless - C_b oxygen concentration in the bulk liquid (mM) - C _b C _b ^* -C_cr (mM) - C _b ^* bulk oxygen concentration in equilibrium with air (mM) - C_cr critical oxygen concentration (mM) - C_s oxygen concentration in the solid phase (mM) - d_p diameter or thickness of a support (cm) - D_eff effective diffusivity of oxygen in the solid phase (cm²/s) - k_m membrane permeability of oxygen (cm/s) - k _m ^* D_eff/_m - k_La_L liquid phase mass transfer rate coefficient (1/s) - k_sa_s solid phase mass transfer rate coefficient (1/s) - (OUR)_v volumetric oxygen uptake rate (mmol O₂/l) - p geometry parameter, p=0 for slab, p=1 for cylinder, p=2 for sphere - P_d oxygen penetration depth (cm) - P _d oxygen penetration depth in the absence of external diffusion limitation (cm) - Q volumetric oxygen uptake rate, (mmol O₂/l·h) - specific oxygen uptake rate (mmol O₂gm biomass (dry)·h) - r length coordinate (cm) - r_c oxygen penetration depth for sphere (cm) - r _c r_c in the absence of external diffusion limitation (cm) - r _c ^* oxygen penetration depth for cylinder (cm) - r _c ^* r _c ^* in the absence of external diffusion limitation (cm) - r_com combined mass transfer rate resistance (s) - r_d location where C_s becomes zero or C_cr (cm) - r_i radius of cylinder or sphere, half thickness of slab (cm) - U_sg superficial gas velocity (cm/s) - X cell concentration (g/l) Greek letters Thiele modulus, dimensionless - _L, _s liquid and solid phase volume fraction, respectively, dimensionless - effectiveness factor On sabbatical leave from KAIST, Seoul, Korea     

Genomic characterization ofCampylobacter jejuni by field inversion gel electrophoresis

The genome ofCampylobacter jejuni was characterized by field inversion gel electrophoresis (FIGE) after digestion with three rare-cutting restriction endonucleases. The restriction enzymesSac II (5-CCGCGG),Sal I (5-GTCGAC), andSma I (5-CCCGGG) were found to produce 13, 5, and 8 fragments respectively from theC. jejuni genome. The fragment sizes ranged from 1.6 kb to 1300 kb, which gaveC. jejuni a genome size of approximately 1900 kb. Furthermore, thegly A and rRNA genes ofC. jejuni were localized to specific fragments by use of Southern analysis, and thegly A gene was shown to be closely linked to one of the three rRNA genes.     

Reaction kinetics of cephalexin synthesizing enzyme from Xanthomonas citri

In enzymatic synthesis of cephalexin from D-alpha-phenylglycine methyl ester (PGM) and 7-amino-3-deacetoxy-cephalosporanic acid (7-ADCA) using alpha-acylamino-beta-lactam acylhydrolase from Xanthomonas citri, it was found that this enzyme catalyzes all three reactions including PGM hydrolysis, cephalexin synthesis, and cephalexin hydrolysis. Based on our experimental results, a mechanistic kinetic model for cephalexin synthesizing enzyme system having acyl-enzyme intermediate was proposed. From this kinetic model, the reaction rate equations for three reactions were derived, and the kinetic parameters were evaluated. A good agreement between the simulation results and the experimental results was found.