Temporal and spatial expression of erbB4 in ectodermal and mesenchymal cells during primary palatogenesis in noncleft and cleft strains of mice

Primary palatogenesis in mice is similar to that in humans, and spontaneous cleft lip appears to be multifactorially determined in both. Binding of a ligand to erbB4 has been shown to stimulate the receptor's protein kinase activity, which subsequently stimulates a signal-transduction cascade leading to cell growth and differentiation, and to morphogenesis during development. In this study, an immunohistochemical technique was used to investigate the temporal and spatial expression of erbB4 in the primary palate of cleft (A/WySn) and noncleft strains of mice (BALB/cBy). Positive staining of erbB4 was found in ectodermal and mesenchymal cells of facial prominences before the primary palate formation stage (day 10, hour 20) in both strains. During the primary palate formation stage (day 11, hour 20), positive staining of erbB4 was found in the ectodermal and mesenchymal cells of the facial prominences of the noncleft strain, but not in those of the cleft strain. These results suggest erbB4 expression may be associated with normal primary palatogenesis of mice and, conversely, cleft lip may be associated with a deficiency of erbB4 expression during primary palate formation in mice.

Calcium channel density and hippocampal cell death with age in long-term culture

The expression of voltage-gated calcium (Ca2+) channel activity in brain cells is known to be important for several aspects of neuronal development. In addition, excessive Ca2+ influx has been linked clearly to neurotoxicity both in vivo and in vitro; however, the temporal relationship between the development of Ca2+ channel activity and neuronal survival is not understood. Over a period spanning 28 d in vitro, progressive increases in high voltage-activated whole-cell Ca2+ current and L-type Ca2+ channel activity were observed in cultured hippocampal neurons. On the basis of single-channel analyses, these increases seem to arise in part from a greater density of functionally available L-type Ca2+ channels. An increase in mRNA for the alpha1 subunit of L-type Ca2+ channels occurred over a similar time course, which suggests that a change in gene expression may underlie the increased channel density. Parallel studies showed that hippocampal neuronal survival over 28 d was inversely related to increasing Ca2+ current density. Chronic treatment of hippocampal neurons with the L-type Ca2+ channel antagonist nimodipine significantly enhanced survival. Together, these results suggest that age-dependent increases in the density of Ca2+ channels might contribute significantly to declining viability of hippocampal neurons. The results also are analogous to patterns seen in neurons of aged animals and therefore raise the possibility that long-term primary neuronal culture could serve as a model for some aspects of aging changes in hippocampal Ca2+ channel function.

Effects of glucose on placental hormones in the human term placenta in vitro

Glucose intake during pregnancy results in a decrease in endogenous insulin-like growth factor binding protein-1 (IGFBP-1). However, the exact role of glucose on placental secretion of IGFBP-1 is unclear. This study was designed to investigate the direct effects of glucose on the production of IGFBP-1 and other placental hormones, using an isolated placental preparation. Using the dual recirculating perfusion system for an isolated human placenta lobule, a total of 43 experiments were performed over a duration of 6 hours. Twenty placentae were perfused with a medium containing 141 +/- 10 mg/dL (7.83 +/- 0.56 mmol/L) glucose (group I) and 23 placentae with 242 +/- 12 mg/dL (13.43 +/- 0.67 mmol/L) glucose (group II). Levels of insulin, glucose, lactate, insulin-like growth factor (IGF-I), IGFBP-1, human placental lactogen (hPL) and beta-human chorionic gonadotropin (beta-hCG) were measured at 30 minute intervals during perfusion. Insulin and IGF-I were barely detectable in the perfusates and their levels were not modulated by glucose. IGFBP-1 was predominantly detected in the maternal rather than the fetal compartment of the placental circulation. Glucose increased the levels of IGFBP-1 in the maternal circulation in groups I and II during the first two hours of perfusion (188 +/- 58% and 193 +/- 31%, respectively). However, during the subsequent 4 hour period, the increase in IGFBP-1 concentration was significantly higher in group II (926 +/- 427%) than in group I (428 +/- 216%) (p < 0.05). There was no difference in the levels of hPL or beta-hCG between the two groups in the maternal circulation. Thus, glucose stimulates the production of IGFBP-1 in the maternal circulation of a placenta in vitro. This increase in IGFBP-1 by glucose in vitro, as opposed to the decrease of IGFBP-1 in vivo, may be due to a lack of circulatory maternal insulin in the isolated placental preparation. These results also suggest that there may be a functional barrier within the placenta that prevents an increase in the level of IGFBP-1 in the fetal circulation.

Functional connectivity of the transected brachial plexus after intercostal neurotization in monkeys

Microsurgical reconstructions of brachial plexuses were performed on twelve monkeys by using ipsilateral intercostal nerves (T3-9). Reinnervation in individual nerves was evaluated monthly by observations of neuromuscular and electromyographic improvements. The electromyographic studies revealed reappearance of motor unit potentials. According to a motor scale ranging from 0 to 4, the mean muscle power 6 months after operation improved to 2.75 in the deltoid muscles, 2 in the biceps muscles, 1.22 in the triceps muscles, 1.13 in the flexor carpi radialis muscles, and 1.6 in the intrinsic muscles of the hands. Retrograde transport of horseradish peroxidase (HRP) from the neuromuscular junctions of the reconstructed musculocutaneous nerves 6 months after complete brachial plexus lesion in four animals demonstrated HRP-labeled neurons in the anterior horns, spinal ganglia and sympathetic ganglia of the thoracic spinal cords. It suggested that the regenerated afferent and efferent circuits in the thoracic cords innervating the transected brachial plexuses were able to generate the movements in the paralyzed upper limbs. However, as evidenced by the behavior patterns and the fact that retrograde-labeled neurons were all found in the thoracic cords, the novel movements observed in the reconstructed brachial plexuses were in synchrony with respiration. These results suggested that the plasticity of central neural networks is limited between two widely separated areas, such as between the midcervical and midthoracic motor cortical areas in the present studies, and therefore, the efforts to reconstruct neural networks, both centrally and peripherally, should aim at rebuilding situations as nearly to the original status as possible.

The importance of determination of jaw position in orthodontic diagnosis and treatment planning for adult patients

The basic data needed for orthodontic diagnosis and treatment planning include color prints of soft tissue facial profile, intraoral dental arches, and occlusion; cephalometric and panoramic radiographs; and dental casts. Hand-wrist and TMJ radiographs are also necessary in some circumstances. If orthodontic diagnosis and treatment plans are made only from the dental alignments and occlusion from the static or hand-assembled dental casts, the diagnosis and treatment planning made may be wrong in some cases. Clinically, it is necessary to find the centric relation of the lower jaw and to transfer the jaw relationship to the articulator. Correct diagnosis and orthodontic treatment planning may then be made from the findings of the occlusal relationship from the articulator accompanied with the information on skeletal age and craniofacial characteristics from the hand-wrist and cephalometric radiographs. Four clinical cases have been presented to demonstrate the importance of determination of jaw position in orthodontic diagnosis and treatment planning in adult patients.

Cytotoxic effects of anthrax lethal toxin on macrophage-like cell line J774A.1

The cytotoxic effects of anthrax lethal toxin purified from an avirulent strain were examined on mouse macrophage-like J774A.1 cells. Cell death induced by high concentration of purified lethal toxin had the characteristics of necrosis. At lower concentrations, the toxin caused no morphological change and most of the cells were viable. Interestingly, apoptotic cells were observed when the cells were preincubated with a serine/threonine phosphatase inhibitor, calyculin A, and then exposed to a toxin concentration of 0.1 microg/ml. This is the first report that lethal toxin of the anthrax bacillus can induce both necrosis and apoptosis and that protein phosphatases are implicated in the regulation of bacterial toxin-induced apoptosis.

[The phagetype and detection of drug-resistance of Salmonella typhi-muriun in Fujian province]

Salmonella typhimurium has accounted for 29.43% of total Salmonella according to the surveillance in Fujian province since 1975. Seven common phagetypes of S. typhimurium were found. The principal phagetype was 7774, which accounted for 46.6% of all phagetypes. S. typhimurium was significantly more resistant to antibiotics in early 1990's than in the 1980's. 57%-72% of the S. typhimurium strains were resistant to aminoglycosides (except amikacin), about 70% were strains resistant to first generation penicillins and tetracyclins while a high proportion of S. typhimurium strains have rapidly become resistant to new broad-spectrum penicillins. The strains of S. typhimurium which are resistant to the first and the second generation of cephalothins become sensitive only to the third generation of cephalo thins. There has been 20% of S. typhimurium strains resistant to some types of quinolones. All S. typhimurium were sensitive to norfloxacin, ofloxacin and ciprofloxacin. In the early 1980's resistant strains to 2-3 kinds of antibiotics accounted for 97%, and nostrains was resistant to more then 6 kinds of antibiotics. In the early 1990's, the strain resistant to 2-3 kinds of antibiotics were less than 20%; while strains resistant to more than 10 kinds of antibiotics were 66%. The increasing rate of resistant strains to antibiotics with widening of drug resistant pattern and the extensive appearance of multiresistant strains have become serious problems to be solved.

Determination of acetylcholine by on-line microdialysis coupled with pre- and post-microbore column enzyme reactors with electrochemical detection

A sensitive procedure consisting of a pre- and post-microbore column reactor sequence of a LC-electrochemical detection system coupled with on-line microdialysis system is described in the present study to measure endogenous acetylcholine concentration in freely moving rats. The pre-column packed, with immobilized choline oxidase and catalase, was used to remove choline, whereas the post-column, packed with immobilized acetylcholine oxidase and choline oxidase, was used to measure acetylcholine selectively. The detection limit of acetylcholine oxidase and choline oxidase, was used to measure acetylcholine selectively. The detection limit of acetylcholine was found to be 5 fmol/microliter (50 fmol/10 microliters). The usefulness of the described methodology was evaluated by examining the change in the striatal acetylcholine concentration of freely moving rats after physostigmine (0.5 mg/kg, s.c.) administration.

High maternal serum free beta-hCG levels in Down syndrome pregnancies: a preliminary report

To investigate the serum free beta-human chorionic gonadotropin (beta-hCG) value in women carrying Down syndrome fetus, we have retrospectively studied 11 Down syndrome pregnancies and 200 singleton unaffected pregnancies between 15 and 22 weeks' gestation. Each affected pregnancy was assigned at least 15 control cases matched with maternal age and gestational age. The median value of free beta-hCG in Down syndrome pregnancies and unaffected pregnancies was 2.56 multiples of the median (MoM) and 1.06 MoM, respectively. The mean free beta-hCG value after log transformation in Down syndrome pregnancies was 2.01 MoM that was significantly different from that of unaffected pregnancies (1.05 MoM, P = 0.024). There were 54.6% (6/11) of Down syndrome pregnancies and 5% (10/200) of unaffected pregnancies with free beta-hCG levels greater than 2.5 MoM. It is suggested that free beta-hCG may be a potentially useful and superior marker in the detection of Down syndrome pregnancies in our population.

[Sequence analyses of Epstein-Barr virus (EBV) Bam HI F DNA fragment in EBV associated diseases]

In order to compare nucleotide differences of Epstein-Barr virus (EBV) Bam HI F DNA fragment from various EBV associated diseases, polymerase chain reactions (PCR) were used to amplify a subfragment (nucleotides 55,381-56,020) of the F fragment from different tissue DNAs, including 20 NPCs, 2 B-cell lymphomas, 2 T-cell lymphomas, 3 infectious mononucleosis (IM), and 3 normal controls. DNA sequences were determined by PCR direct sequencing or sequencing after DNA cloning. The PCR products were cloned into pGEM-3Z vector, then the resulting recombinant plasmids were used to transform DH5 alpha competent cells. Plasmid DNAs from the correct transformants were prepared for DNA sequencing. The results showed that the proportion of the f variant in NPCs, B-cell lymphomas, T-cell lymphomas, IMs, and normals were 40%, 0%, 0%, 33%, and 33%, respectively. Because the f variant was not specifically more prevalent in NPC tissues compared to the non-tumor tissues, we speculate that there is no strong association between the f variant and NPC. These results were different from other reports. Coinfection of the F strain and the f variant was found both in some NPC patients and normal individuals. Analyses of Bam HI F subfragments of 35 EBV isolates from the 30 tissue DNAs revealed that there were changes at four corresponding positions of the B95-8 strain. They were nucleotide T at 55,473 replaced by G, an insertion of TGT after nucleotide 55,543, nucleotide A at 55,564 replaced by G, and nucleotide T at 55,958 replaced by C. These 4 nucleotide changes may confer a character of Taiwan strains. The nucleotides of the F strain at coordinates 55,519, 55,596, 55,680, 55,703, and 55,895 were T, T, A, A, and C, and those for the f variant were C, C, C, C, and T. These two patterns were not correlated with types A and B of EBV.

Hyperglycemia induced activation of type-1 protein phosphatase activator (kinase FA) in perfused human placenta

We report the identification of type-1 protein phosphatase activating factor (kinase FA), a unique biologic mediator for both insulin and epidermal growth factors in the human placenta. The activity of kinase F, was found to be extremely labile in the unperfused placenta. Fresh term placentas lost more than 50% of the total kinase FA activity within 6 hours when exposed to air of incubated in medium but not perfused. In contrast, the activity of kinase FA was stable when the human term placenta was dually perfused. This indicates that placental dual perfusion is a useful method for studying protein phosphorylation-dephosphorylation involved in signal transduction. When fresh placentas were perfused with media containing glucose at 141 +/- 10, 242 +/- 12 and 436 +/- 20 mg/dL, kinase FA activity was stimulated several-fold in a glucose concentration-dependent manner when compared with control levels at delivery. The results suggest that hyperglycemia-mediated activation may represent a previously unknown control mechanisms for the regulation of protein kinase FA. The results also suggest that human placental perfusion is a good in vitro system for studying signal transduction mechanisms involved in hormonal actions and metabolic regulation.

Allelic deletion mapping of putative tumor suppressor genes on 17q in sporadic ovarian cancer

OBJECTIVES

1) To study whether the same or different chromosome 17q genes may be involved in the oncogenesis of familial and sporadic ovarian malignancies. 2) To localize the candidate gene in the sporadic ovarian cancers.

METHODS (STUDY DESIGN)

Using DNA extracted from ovarian tumors and corresponding peripheral leukocyte, we examined the status of loss of heterozygosity (LOH) at 12 loci spanning chromosome 17q12-q25 by Southern hybridization and polymerase chain reaction.

RESULTS

Comparison of the extent of LOH among 25 epithelial ovarian tumors showing allele loss at one or more loci on 17q, the smallest overlapping region of allelic deletion is between D17S579 and GIP, with a genetic distance of approximate 2 cM.

CONCLUSIONS

From our allelic deletion analysis of chromosome 17q loci, it indicates that there are more than one ovarian cancer candidate genes on chromosome 17q.

Distribution of p21ras during primary palate formation of non-cleft and cleft strains of mice

Cleft lip, with or without cleft palate, is one of the most common defects in craniofacial formation. The primary palatogenesis of mice is similar to that of humans and spontaneous cleft lip is associated with genotype in both mice and humans. To investigate the temporal and spatial expression of ras genes in cleft (A/WySn) and non-cleft strains of mice (BALB/cBy), a broad spectrum ras antibody was used. Positive staining was found in ectodermal, mesenchymal, and neuroepithelial cells of facial prominences before the primary palate formation stage (10 d 20 hr) in both strains. During the primary palate formation stage (11 d 20 hr), positive staining was found in the ectodermal and mesenchymal cells of the facial prominences of the non-cleft strain but not in those of the cleft strain. These results suggest ras genes may play a role in the primary palatogenesis of mice. Cleft lip could be associated with the deficiency of ras gene expression during primary palate formation of mice.

Identification of a human homologue of yeast nuc2 which interacts with the retinoblastoma protein in a specific manner

The full-length cDNA clone which encodes a novel 824-amino acid protein was characterized. The predicted protein contains ten 34-amino acid repeats characteristic of the tetratricopeptide repeat protein family. The sequence homology and organization of the 10 repeats are similar to those of the nuc2 protein of fission yeast and bimA protein of Aspergillus, which suggests that the newly identified protein could be the human homologue of nuc2 (H-NUC). Consistent with this notion, the M(r) 95,000 H-NUC is a nuclear protein with DNA binding activity. This protein binds to hypophosphorylated Rb protein in a region indistinguishable from that to which SV40 large T antigen binds. However, Rb also binds to H-NUC at the tetratricopeptide repeat motif, a region which contains sequences different from the binding motifs of either T-antigen or E2F-1. To mimic the temperature-sensitive mutant of yeast nuc2, an H-NUC mutant was made in which the highly conserved glycine 640 residue was changed to aspartic acid. In contrast to wild-type H-NUC, the mutant was temperature sensitive in binding to Rb protein. These results, taken together, suggest that the interaction between H-NUC and Rb may be significant.

Maternal serum alpha-fetoprotein levels between 13 and 24 weeks' gestation

Maternal serum alpha-fetoprotein (MSAFP) screening has been widely used and proven valuable in the prediction of a variety of fetal disorders. Any laboratory intending to provide MSAFP screening needs to establish its own reference data. In order to establish a normal MSAFP median value at our own laboratory, 5256 samples of MSAFP were collected from uncomplicated, singleton pregnant women between 13 and 24 weeks' gestation. The MSAFP median levels steadily rise with advancing gestation about 16% per gestational week in average. There were 0.17% and 4.4% of the pregnancies with serum AFP levels less than 0.25 multiple of the median (MoM) and 0.5 MoM respectively, and 4.22% and 1.66% with serum levels above 2.0 MoM and 2.5 MoM. Accurate and satisfactory interpretation of MSAFP screening should be emphasized in the establishment of a well-developed normal median value.

Molecular characterization of a novel human gene, SEC13R, related to the yeast secretory pathway gene SEC13, and mapping to a conserved linkage group on human chromosome 3p24-p25 and mouse chromosome 6

We previously described sequence tags from 58 novel directionally cloned human cDNAs from an enriched retinal pigment epithelial cell line library (Gieser and Swaroop, 1992). The nucleotide sequence of one of the cDNA clones, AA35 (D3S1231E), showed strong homology to the yeast SEC13 gene, required for vesicle biogenesis from endoplasmic reticulum during the transport of proteins. We have designated the human gene SEC13R (SEC13-Related). The amino acid sequence of the SEC13R gene product shows 70% similarity to yeast Sec13p, suggesting that SEC13R may be the human homolog of SEC13. The deduced polypeptide sequence contains several beta-transducin like 'WD40' repeats, and is rich in serine and threonine residues. The 1.4 kb transcript of SEC13R is detected by Northern analysis in many human tissues. However, RT-PCR analysis using two primer sets from different regions of the gene suggests differential expression of alternately spliced transcripts in various tissues. Somatic cell hybrid and in situ hybridization studies localized the SEC13R gene to human chromosome 3p24-p25. A related sequence was mapped to chromosome 18q11.2-q12. SEC13R was physically mapped to a yeast artificial chromosome (YAC) clone spanning the D3S720 marker from the region of the Von Hippel-Lindau disease locus. The mouse Sec13r gene was mapped to the conserved linkage group on chromosome 6 that corresponds to human chromosome 3p24-p25.

Effects of sodium butyrate on the transfer of arachidonic acid to phosphatidylcholine in a clonal oligodendrocyte cell line (CB-II)

The effect of sodium butyrate on membrane phospholipid metabolism in a neonate rat cerebellum derived clonal oligodendrocyte cell line (CB-II) was investigated. Sodium butyrate is an agent known to induce cell differentiation and morphological transformations. A comparison of the in vivo phospholipid labeling patterns obtained by incubating CB-II cells with [3H]choline, [14C]myristic acid or [3H]arachidonic acid indicated that butyrate altered the route of acylation-deacylation in phosphatidylcholine (PC) biosynthesis. Using an in vitro incubation system containing homogenates of CB-II cells, the largest proportion of radioactivity was found in PC, and addition of sodium butyrate resulted in a further increase in the transfer of arachidonic acid to PC, but not to phosphatidylinositol. Similar results were obtained when this in vitro acylation activity was tested using homogenates from sodium butyrate pretreated cells. The butyrate effect was observed regardless of whether or not exogenous lysophosphatidylcholine (LPC) was added to the incubation system. Addition of butyrate did not result in a change in the activity of LPC:acyl-CoA (coenzyme A) acyltransferase (EC 2.3.1.23) in CB-II cells upon incubating cell homogenates with [1-14C]arachidonoyl-CoA and LPC. However, when cell homogenates were incubated with [3H]arachidonic acid in the presence of 2.5-10 mM sodium butyrate, arachidonoyl-CoA synthesis was stimulated. A time course study demonstrated that significant stimulation occurred after three minutes. Taken together, the results suggest that in CB-II cells, sodium butyrate stimulates the transfer of arachidonic acid into PC and that this effect is at least partially due to a stimulation of arachidonoyl-CoA ligase (EC 6.2.1.3).

11 alpha-hydroxylation of progesterone using modified alginate-immobilized cells

The major disadvantage of using alginate-immobilized Aspergillus ochraceus for 11 alpha-hydroxylation of progesterone is its instability in phosphate solutions. In this study, different gel-hardening methods were used to improve the stability of alginate gels. Addition of Fe3+ and Fe2+ ions increased the activity of hydroxylation, but Fe2+ was not a good gelling agent. Replacement of CaCl2 by FeCl3 as the gelling agent increased the activity of the immobilized cells by about 33%. Hardening the alginate-immobilized cells with polyacrylamide (PAA) increased their stability in a 0.1 M phosphate buffer from 0.35 h to over 36 h. The productivity was increased by a factor of 1.8 compared to those without hardening, and the maximum yield was also increased from 84.3% to 90.8%. The physical properties and biocatalytic characteristics of PAA-hardened, immobilized cells were found to be feasible for application in a steroid bioconversion system.

11 alpha-Hydroxylation of progesterone in biphasic media using alginate-entrapped Aspergillus ochraceus gel beads coated with polyurea

A novel cell-immobilization technique was developed in this study for increasing substrate partition to the gel matrix by coating a polyurea thin layer on the surface of Ca-alginate beads. The proposed method was simple and could be performed under mild conditions. The bioconversion of progesterone to 11 alpha-hydroxyprogesterone with these polyurea-coating alginate-entrapped Aspergillus ochraceus cells was investigated using different organic solvents in biphasic media. The reaction medium of ethyl acetate could markedly enhance the bioconversion rate with the existence of a hydrophobic layer, most likely resulting from the increasing partition of substrate to gel matrix. Bioconversion with higher substrate concentration was possible using an ethyl acetate-water medium. The conversion rate increased almost linearly with increasing substrate concentration from 10 to 80 g l-1. The rate with 80 g l-1 progesterone increased up to six times greater than the rate with the immobilized cells without coating, and also exhibited a much higher rate than that reported in the literature.

Fluorescent spot test method for specific detection of beta-lactamases

A simple, sensitive fluorescent spot test method for specific detection of microbial beta-lactamases has been developed, based on the modification of a previously disclosed method (K. C. S. Chen, October 23, 1990, U.S. Patent 4,965,193). The new fluorescence developer used in the present study consisted of 0.5 mM HgCl2, in 0.5 M sodium citrate buffer, pH 4.5, prepared in 0.5% formaldehyde aqueous solution. A beta-lactam substrate solution consisting of a beta-lactam antibiotic with an acyl side chain containing an alpha-amino group and an alpha-phenyl group, or its derivatives, was incubated with a beta-lactamase-producing organism. One volume of the fluorescence developer was added to 4 vol of the incubated beta-lactam substrate solution, followed by heating the mixture at 45 degrees C for 10 min. The mixture was spotted on filter paper. Production of fluorophore indicated beta-lactamase activity. Each fluorophore was analyzed by TLC and its chemical identity was determined. Using ampicillin as the penicillinase substrate and cephalexin as the cephalosporinase substrate, the new method can be conveniently carried out by using dropping bottles for storing and dispensing the substrate solutions and the fluorescence developer. This modified method also provided more favorable conditions for the penicillinases to remain active during fluorescence development. Therefore, the sensitivity of the test was increased.

Deep vein thrombosis during pregnancy

Antepartum deep vein thrombosis is quite rare in Chinese women during pregnancy. An adequate diagnosis and early treatment are extremely important as the deep vein thrombosis can embolize, in particular, to the pulmonary vasculature. We present a case of pregnancy at 36 weeks gestation complicated by deep vein thrombosis. The objective diagnosis of deep vein thrombosis for obstetric patients is the noninvasive Doppler ultrasound and plethysmography. An early diagnosis is important to reduce maternal and fetal risks related to embolization. Continuous therapy of low dose intravenous heparin is safe and effective during pregnancy.

Allelic loss in ovarian cancer

Loss of heterozygosity (LOH) was examined at 86 loci distributed on every chromosomal arm in 50 human ovarian tumors. Frequent allele losses were observed on chromosomes 13q (42%), 17p (42%), 17q (45%), and Xp (41%). Deletion mapping on chromosome 17 revealed a candidate gene on the long arm distal to D17S41/S74 for ovarian cancer which is distant from the locus for early onset breast cancer. LOH on chromosome 17q was found to be concordant with LOH on chromosomes 3p, 13q, 17p and Xp suggesting that it may be an early event in neoplastic development. These findings indicate that multiple tumor-suppressor genes for ovarian cancer possibly exist on chromosomes 13q, 17, and/or Xp and provide the basis for the identification of candidate gene(s) associated with ovarian cancer. The chromosomal mechanisms resulting in allele losses in ovarian cancer include deletion, deletion/duplication, mitotic recombination and monosomy, in concordance with the developed genetic model.

The evolutionary history of the first three enzymes in pyrimidine biosynthesis

Some metabolic pathways are nearly ubiquitous among organisms: the genes encoding the enzymes for such pathways must therefore be ancient and essential. De novo pyrimidine biosynthesis is an example of one such metabolic pathway. In animals a single protein called CAD carries the first three steps of this pathway. The same three enzymes in prokaryotes are associated with separate proteins. The CAD gene appears to have evolved through a process of gene duplication and DNA rearrangement, leading to an in-frame gene fusion encoding a chimeric protein. A driving force for the creation of eukaryotic genes encoding multienzymatic proteins such as CAD may be the advantage of coordinate expression of enzymes catalyzing steps in a biosynthetic pathway. The analogous structure in bacteria is the operon. Differences in the translational mechanisms of eukaryotes and prokaryotes may have dictated the different strategies used by organisms to evolve coordinately regulated genes.