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Biomedical subjects

D Zhang

Publications and source records attributed to D Zhang.

At least 361 records · Page 20Linked to original sources
PubMed1998

Effects of conformationally restricted synthetic retinoids on ovarian tumor cell growth.

We have used conformationally restricted retinoids to investigate the role of individual RAR subtypes and RXR in mediating the growth response of ovarian tumor cells to retinoids. Our results show that treatment of all-trans-RA-sensitive CAOV-3 cells with retinoids that bind and activate a single RAR or RXR led to a partial inhibition of growth. Treatment of all-trans-RA- resistant SKOV-3 cells did not alter growth. Maximum inhibition of growth, comparable to that observed following treatment with natural retinoids such as all-trans-RA and 9-cis-RA, was obtained only following treatment with a combination of an RAR-selective compound and an RXR-selective one. These results suggest that activation of both RAR and RXR classes is required in order to obtain maximum inhibition of ovarian tumor cell growth by retinoids. In addition, one compound, AHPN, was found to inhibit both RA-sensitive CAOV-3 and RA-resistant SKOV-3 cells. Further study of the effects of this retinoid showed that AHPN acts through an apoptotic pathway. Taken together, our results suggest that retinoids may serve as effective anti-proliferative agents in the treatment of ovarian cancer.

Apoptosis↗
PubMed1998

Cloning and characterization of mouse GABA(C) receptor subunits.

Retinal gamma-aminobutyric acid type C (GABA[C]) receptors are believed to consist of rho subunits. The pharmacological properties of GABA(C) receptors appear to vary among different species. Since the mouse is an important model for gene targeting and behavioral studies, this study was aimed at cloning rho subunits in the mouse. Here we report the isolation of two full length cDNAs corresponding to mouse rho1 and rho2 subunits. In contrast to the rat, both subunits in mouse are able to form homomeric receptors, but only rho2 receptors are insensitive to picrotoxinin. Mouse rho1 and rho2 also co-assemble to form heteromeric receptors. These findings form the basis for further study on GABA(C) receptors using the mouse model.

Amino Acid Sequence↗
PubMed1998

Human RPA (hSSB) interacts with EBNA1, the latent origin binding protein of Epstein-Barr virus.

RPA is the replicative single-strand DNA (ssDNA) binding protein of eukaryotic chromosomes. This report shows that human RPA interacts with EBNA1, the latent origin binding protein of Epstein-Barr virus (EBV). RPA binds to EBNA1 both in solution, and when EBNA1 is bound to the EBV origin. RPA is a heterotrimer, and the main contact with EBNA1 is formed through the 70 kDa subunit of RPA, the subunit which binds to ssDNA. We propose that this interaction between RPA and EBNA1 is an early step in activation of the latent origin of EBV.

DNA, Viral↗
PubMed1998

Feasibility of pylorus-preserving gastrectomy with a wider scope of lymphadenectomy.

OBJECTIVE: To demonstrate the feasibility and safety of pylorus-preserving gastrectomy (PPG) accompanied by complete suprapyloric and infrapyloric lymph node dissection. DESIGN: Retrospective review. SETTING: A university hospital in Japan. PATIENTS: Fifteen patients underwent PPG, and 28 patients underwent conventional distal gastrectomy (CDG) with Billroth I anastomosis. All patients had early gastric cancer, with either limited invasion in the mucosal layer or invasion into the submucosal layer. INTERVENTIONS: In the PPG procedure, the distal part of the stomach was resected while retaining a 1.5-cm pyloric cuff. The right gastroepiploic artery, the right gastric artery, and hepatic and pyloric branches of the vagus nerve were divided, and the infrapyloric artery was preserved. A modified D1 or D2 lymphadenectomy accompanied the PPG. MAIN OUTCOME MEASURES: Patients undergoing the PPG and CDG procedures were assessed 1 year after their surgical procedure. Changes in body weight, serum total protein levels, and serum albumin levels, the incidence of dumping syndromes, and endoscopic findings in the gastric remnant were compared between the 2 groups. RESULTS: Weight loss was significantly less in the PPG group than in the CDG group (P=.02). The incidences of early dumping syndromes, especially vasomotor symptoms, were significantly lower in the PPG group than in the CDG group (P=.03 and P=.02, respectively). The pyloric sphincter function was preserved, and there was no anastomotic leakage in the PPG group. CONCLUSIONS: The PPG procedure with complete D2 lymphadenectomy can be performed safely with a low incidence of major complications and a better postoperative outcome than the CDG procedure. The PPG procedure can be recommended for the treatment of early gastric cancer with broader indications.

Aged↗
PubMed1998

Multigenic control of lupus-associated antiphospholipid syndrome in a model of (NZW x BXSB) F1 mice.

In a subset of systemic lupus erythematosus (SLE) patients, antiphospholipid syndrome, characterized by occurrence of anti-cardiolipin (CL) antibodies, thrombocytopenia, thrombosis and recurrent intrauterine fetal death occurs. Male (NZW x BXSB)F1 mice, carrying the BXSB Yaa gene, serve as a model for SLE-associated antiphospholipid syndrome. Using microsatellite markers in the NZW x (NZW x BXSB)F1 backcross male progeny, we mapped BXSB alleles contributing to the generation of anti-CL antibodies, platelet-binding antibodies, thrombocytopenia and myocardial infarction. Generation of each disease character was controlled by two major independently segregating dominant alleles, i.e. those on chromosomes (Chr.) 4 and 17 for anti-CL antibodies, Chr. 8 and 17 for both anti-platelet antibodies and thrombocytopenia and, to our surprise, Chr. 7 and 14 for myocardial infarction, and that a combination of the two alleles appeared to produce full expression of each character, as a complementary gene action. The alleles on Chr. 17 linked to the above three characters were all mapped in close proximity to the H-2 complex. Therefore, no single factor such as anti-CL antibodies can explain the pathogenesis of SLE-associated antiphospholipid syndrome. Rather, a combination of susceptibility alleles such as described here, along with additional modifying loci, i.e. BXSB Yaa and some from NZW, characterizes unique SLE features in male (NZW x BXSB) F1 mice. There are potentially important candidate genes which may be linked to the syndrome.

Animals↗
PubMed1998

Isolation and characterization of Enterobacter cloacae capable of metabolizing asparagine.

A gram-negative, rod-shaped bacterium capable of utilizing L-asparagine as its sole source of carbon and nitrogen was isolated from soil and identified as Enterobacter cloacae. An intracellularly expressed L-asparaginase was detected and it deaminated L-asparagine to aspartic acid and ammonia. High-pressure liquid chromatography analysis of a cell-free asparaginase reaction mixture indicated that 2.8 mM L-asparagine was hydrolyzed to 2.2 and 2.8 mM aspartic acid and ammonia, respectively, within 20 min of incubation. High asparaginase activity was found in cells cultured on L-fructose, D-galactose, saccharose, or maltose, and in cells cultured on L-asparagine as the sole nitrogen source. The pH and temperature optimum of L-asparaginase was 8.5 and 37-42 degrees C, respectively. The half-life of the enzyme at 30 degrees C and 37 degrees C was 10 and 8 h, respectively.

Asparaginase↗
PubMed1998

Microplitis croceipes teratocytes: in vitro culture and biological activity of teratocyte secreted protein.

Teratocytes originate from the dissociation of the extraembryonic serosal membrane in some Braconidae and Scelionidae. Methods used to culture teratocytes in vitro are described and the yield of teratocyte secreted proteins (TSP) was measured. Although 90% are viable after 6 days, in vitro teratocytes reached only half the diameter (32&mgr;m) of the same age teratocytes obtained in vivo. Teratocytes cultured in vitro secrete as much as 0.7&mgr;g of protein per day per larval equivalent ( approximately 900 cells). Presence of parasitoid larvae enhanced teratocyte viability while periodic exchange of medium did not. However, medium exchange significantly increased the total amount of protein secreted. Size and viability were improved with the addition of 10% FBS to the Ex-cell 400 culture medium. Non-denaturing PAGE showed at least 15 proteins with molecular sizes estimated to be between 24 to 347kDa in medium containing teratocytes. An in vitro fat body assay was developed to measure the effect of TSP on protein synthesis and juvenile hormone esterase (JHE) activity. Crude TSP inhibited in vitro incorporation of [(35)S]-methionine into protein synthesized by the fat body. The amount of JHE released from in vitro fat body treated with crude TSP was significantly less than controls, most likely caused by the inhibition of general protein synthesis. The active fraction of TSP passed through a 30kDa molecular weight cutoff filter but was retained by a 3kDa filter. SDS-PAGE revealed four proteins with molecular weights between 8 and 20kDa not present in control medium incubated without teratocytes.

Journal Article↗
PubMed1998

Polygalasaponins XLII-XLVI from roots of Polygala glomerata.

Five new oleanane-type saponins, polygalasaponins XLII-XLVI, along with two known saponins were isolated from the roots of Polygala glomerata Lour. The structures of polygalasaponins XLII-XLVI were elucidated as 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl- (1-->2)-{4-O-[(E)-3,4-dimethoxycinnamoyl]}-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)- alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-arabinopyranosyl- (1-->3)]-[4-O-(E)-p-methoxycinnamoyl]-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)- alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl- (1-->3)]-{4-O-[(E)-3,4-dimethoxycinnamoyl]}-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)- alpha-L-rhamnopyranosyl-(1-->2)-[6-O- acetyl-beta-D-glucopyranosyl-(1-->3)]-{4-O- [(E)-3,4-dimethoxycinnamoyl]}-beta-D-fucopyranosyl ester, 3-O-beta-D- glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->4)- beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl- (1-->2)-[6-O-acetyl-beta-D-glucopyranosyl-(1-->3)]-{4-O-[(Z)-3, 4-dimethoxycinnamoyl]}-beta-D-fucopyranosyl ester, respectively, on the basis of spectroscopic and chemical evidence.

Carbohydrate Sequence↗
PubMed1998

Oligosaccharide polyesters from roots of Polygala glomerata.

Seven new sucrose and oligosaccharide esters, glomeratoses A-G, together with four known compounds, 3-O-[(E)-3,4,5-trimethoxycinnamoyl]-beta-D-fructofuranosyl-(2-->1) - (6-O-benzoyl)-alpha-D-glucopyranoside, 3-O-(E)-sinapoyl-beta-D-fructofuranosyl-(2-->1)-[6-O-(E)-sinapo yl]-alpha-D- glucopyranoside, tenuifoliside C and reiniose G were isolated from the roots of Polygala glomerata. Glomeratoses A-G were elucidated as 3-O-[(E)-3,4,5-trimethoxycinnamoyl]-beta-D-fructofuranosyl-(2-->1) -alpha-D- glucopyranoside, 3-O-(E)-sinapoyl-beta-D-fructofuranosyl-(2-->1)-[6-O-(E)-p- coumaroyl]-alpha-D-glucopyranoside, 3-O-[(E)-3,4,5-trimethoxycinnamoyl]-beta-D-fructofuranosyl-(2-->1) -[6-O-(E)- p-coumaroyl]-alpha-D-glucopyranoside, 3-O-[(E)-3,4,5-trimethoxycinnamoyl]-beta-D-fructofuranosyl-(2-->1) -[6-O-(E)- 3,4,5-trimethoxycinnamoyl]-alpha-D-glucopyranoside, 1-O-{6-O-[3-O-(E,E)-(beta, beta'-bis-sinapoyl)-beta-D-fructofuranosyl]}-alpha- D-glucopyranoside intramolecular ester, 1-O-(E)-p-coumaroyl-(3-O-benzoyl)-beta-D- fructofuranosyl-(2-->1)-[beta-D-glucopyranosyl-(1-->2)]-[6-O-acetyl-beta -D- glucopyranoysl-(1-->3)]-[4-O-(E)-feruloyl]-(6-D-acetyl)-alph a-D- glucopyranoside, 1-O-(E)-p-coumaroyl-(3-O-benzoyl)-beta-D-fructofuranosyl-(2-->1)-[ beta-D- glucopyranosyl-(1-->2)]-[6-O-acetyl-beta-D-glucopyranoside-(1-->3)]-{4-O - [4-O-beta-D-glucopyranosyl-(E)-feruloyl]}-[6-O-(E)-p-coumaroyl+ ++]-alpha- D-glucopyranosyl, respectively, on the basis of chemical and spectral evidence.

Carbohydrate Conformation↗
PubMed1998

A class III acidic endochitinase is specifically expressed in the developing seeds of soybean (Glycine max [L.] Merr.).

A soybean chitinase which has an apparent molecular mass of 28 kDa by SDS-PAGE, and has chitinase specific activity of 133 units per mg protein at pH 5.2 and an apparent pI of 5.7, was purified from mature dry seeds. Based upon the selected part (the residue positions 10-17) of the determined N-terminal 38 amino acid sequence, a 23-mer degenerate oligonucleotide was synthesized and used for the PCR cloning of the chitinase cDNA. The resulting 1340 bp cDNA was comprised of a 5'-untranslated region of 39 bases, a coding region corresponding to a 25 amino acid signal sequence, followed by a mature 308 amino acid sequence (calculated molecular mass 34,269, calculated pI 4.7), and a 235 nucleotide 3'-terminal untranslated region including 24 bases of the poly(A) tail. By comparing the deduced primary sequence with those of plant chitinases known to date, this enzyme was more than 50% identical to every class III acidic chitinase, but has no significant similarity to other families of chitinases. The comparison also showed that the C-terminal region of this chitinase is markedly extended, by at least 31 residues. Northern blot analysis demonstrated that this mRNA species is remarkably transcribed from the early stage until the late middle stage of seed development, whilst it is hardly expressed in the leaves and the stems of soybean. Spatial and temporal expression of this single gene imply that this class III chitinase is mainly devoted to the seed defense, not only in development but also in dormancy of soybean seed. This is the first reported isolation and cDNA cloning of a class III acidic endochitinase from seeds. According to the chitinase nomenclature we propose that this enzyme would be classified into a new class of chitinase PR-8 family, together with a Sesbania homologue.

Amino Acid Sequence↗
PubMed1998

R-deprenyl and R-2-heptyl-N-methylpropargylamine prevent apoptosis in cerebellar granule neurons induced by cytosine arabinoside but not low extracellular potassium.

R-Deprenyl and R-2-heptyl-N-methylpropargylamine (R-2-HMP) are compounds that have been shown to reduce neuronal death in various in vitro and in vivo models involving apoptosis but do not always prevent apoptosis. In the present study we have examined the effects of these compounds and their S enantiomers on cytosine arabinoside (ara C)-induced apoptosis and low K+-induced apoptosis in cerebellar granule cells in primary culture. It was found that R-deprenyl and R-2-HMP could prevent ara C-induced apoptosis with an EC50 around 10(-9) M but could not prevent low K+-induced apoptosis. S-Deprenyl and S-2-HMP did not prevent apoptosis under any conditions but were found to antagonize the antiapoptotic actions of R-deprenyl and R-2-HMP. Using the fluorescent mitochondrial dye chloromethyltetramethylrhodamine methyl ester it was found that there was a loss of mitochondrial function in cerebellar granule cells exposed to ara C but not low K + medium. R-Deprenyl and R-2-HMP prevented the ara C-induced loss of mitochondrial function. It is concluded that R-deprenyl and R-2-HMP prevent apoptosis of cerebellar granule cells by a mechanism that is independent of monoamine oxidase inhibition and that they act on the same site to prevent specifically apoptosis involving a loss of mitochondrial membrane potential, possibly p53-dependent apoptosis.

Animals↗
PubMed1998

Information sources and barriers to cancer treatment by racial/ethnic minority status of patients.

BACKGROUND: This study examined the sources used by cancer patients to obtain helpful information regarding their treatment options and side effects and the major predictors that facilitated usage of information. METHODS: The survey was administered to a representative sample of cancer patients in Texas. The cancer treatment facilities from which the patients were sampled were part of the University of Texas M. D. Anderson Cancer Center's Texas Community Oncology Network. A total of 593 patients (65%) out of 910 contacted responded to the survey. RESULTS: The patients reported that providers such as physicians and nurses were the most helpful sources of information. White patients tended to use books and reference materials more heavily to gather additional information regarding their treatment, while black patients relied on pamphlets and television. Educational level appeared to have a major influence on the black patient's use of printed materials. CONCLUSIONS: The results document the important role that providers play in influencing patients' treatment decisions. Effective ways to communicate with cancer patients are different for patients with different racial backgrounds. Implications for the future development of patient education materials and cancer prevention initiatives targeting ethnic minorities are addressed.

Adult↗
PubMed1998

Role of calciotrophic hormones in calcium mobilization of lactation.

The postpartum period can be a time when profound changes in calcium metabolism and bone mineral density (BMD) occur, particularly in association with lactation. We investigated the hypothesis that calciotrophic hormones [1,25-dihydroxyvitamin D, 25-hydroxyvitamin D, and parathyroid hormone (PTH)] are different by lactation practice or hormone status [PTH-related peptide (PTHrP), estradiol, and prolactin] and have a potential role in the bone loss and recovery associated with lactation. 1,25-Dihydroxyvitamin D, 25-hydroxyvitamin D, PTH, femoral BMD, PTHrP, prolactin, estradiol, and bone turnover markers were measured at 2 wk and at 2, 4, 6, 12, and 18 mo postparturition in 115 postpartum women aged 20-40 y (parity: 0-1). Lumbar spine BMD was measured at 2 wk and at 6, 12, and 18 mo during the postpartum period. PTH, 1,25-dihydroxyvitamin D, and 25-hydroxyvitamin D concentrations were nonlinear across the 18-mo postpartum period. Between baseline and 18 mo postparturition, PTH and 1,25-dihydroxyvitamin D concentrations did not decline, while there was a substantial decline in 25-hydroxyvitamin D concentrations. PTH, 1,25-dihydroxyvitamin D, and 25-hydroxyvitamin D concentrations did not differ by lactation practice or by PTHrP, estradiol, or prolactin status. These classic calciotrophic hormones were not associated with concentrations of bone turnover markers or changes in BMD in lactating women. In summary, patterns of change in calciotrophic hormones (PTH, 1,25-dihydroxyvitamin D, and 25-hydroxyvitamin D) in the 18-mo postpartum period appeared to be independent of PTHrP, estradiol, prolactin, or lactation status and were not associated with bone turnover markers. These data do not support the hypothesis that these three calciotrophic hormones are a central part of the calcium mobilization associated with the bone loss of lactation.

Adult↗
PubMed1998

Dissection of the effects of tumor necrosis factor-alpha and class II gene polymorphisms within the MHC on murine systemic lupus erythematosus (SLE).

Gene(s) in the MHC of the NZW strain (H-2z) up-regulate(s) systemic lupus erythematosus (SLE) in (NZB x NZW) F1 mice. So far, two plausible mechanisms have been implicated: (i) unique mixed haplotype class II molecules formed in the F1 mice act as a restriction element for self-reactive T cells and (ii) a unique polymorphism in the H-2-linked NZW tumor necrosis factor (TNF)-alpha allele which down-regulates TNF-alpha is contributory. Because of the difficulty in dissecting these alleles within the H-2 complex, it has not been determined which is indeed the case. We addressed this issue by establishing three different H-2-congenic (NZB x NZW) F1 mice bearing distinct haplotypes at class II and TNF-alpha regions, i.e. (NZB x NZW) F1 (H-2d/z:A(d/u)E(d/u)TNF(d/z)), (NZB x NZW.PL) F1 (H-2(d/u):A(d/u)E(d/u)TNF(d/d)) and (NZB x NZW.H-2d) F1 (H-2(d/d):A(d/d)E(d/d)TNF(d/d)). Among these, only (NZB x NZW) F1 produced a markedly lower level of TNF-alpha, due to the unique NZW TNF-alpha allele (TNF(z)). Studies of anti-DNA antibodies and lupus nephritis revealed that, compared to (NZB x NZW) F1, the disease of (NZB x NZW.H-2d) F1 was markedly reduced. In (NZB x NZW.PL) F1, the onset of renal disease was significantly delayed, while the extent of proteinuria and renal histopathology in individuals that had developed the disease was comparable to that seen in (NZB x NZW) F1. It seems likely that both class II and TNF-alpha gene polymorphisms are functioning as H-2-linked predisposing genetic elements, and that the TNF-alpha polymorphism acts to modulate an initial process of the renal disease.

Animals↗
PubMed1998

Estimates of the peak pressures in bone pore water.

The maximum pore fluid pressures due to uniaxial compression are determined for both the vascular porosity (Haversian and Volkmann's canals) and the lacunar-canalicular porosity of live cortical bone. It is estimated that the peak pore water pressure will be 19 percent of the applied axial stress in the vascular porosity and 12 percent of the applied axial stress in the lacunar-canalicular porosity for an impulsive step loading. However, the estimated relaxation time for the vascular porosity (1.36 microseconds) is three orders of magnitude faster than that estimated for the lacunar-canalicular porosity (4.9 ms). Thus, under physiological loading, which has a stress rise time generally larger than 1 ms, pressures higher than the vascular pressure cannot be sustained in the vascular porosity due to the swift pressure relaxation in this porosity (unless the fluid drainage through the boundary is obstructed). The model also predicts a slight hydraulic stiffening of the bulk modulus due to longer draining time of the lacunar-canalicular porosity. The undrained bulk modulus is 6 percent higher than the drained bulk modulus in this case.

Cell Membrane Permeability↗
PubMed1998

A Ras-dependent pathway regulates RNA polymerase II phosphorylation in cardiac myocytes: implications for cardiac hypertrophy.

Despite extensive evidence implicating Ras in cardiac muscle hypertrophy, the mechanisms involved are unclear. We previously reported that Ras, through an effector-like function of Ras GTPase-activating protein (GAP) in neonatal cardiac myocytes (M. Abdellatif et al., J. Biol. Chem. 269:15423-15426, 1994; M. Abdellatif and M. D. Schneider, J. Biol. Chem. 272:527-533, 1997), can up-regulate expression from a comprehensive set of promoters, including both cardiac cell-specific and constitutive ones. To investigate the mechanism(s) underlying these earlier findings, we have used recombinant adenoviruses harboring a dominant negative Ras (17N Ras) allele or the N-terminal domain of GAP (nGAP), responsible for the Ras-like effector function. Inhibition of endogenous Ras reduced basal levels of [3H]uridine and [3H]phenylalanine incorporation into total RNA, mRNA, and protein, with parallel changes in apparent cell size. In addition, 17N Ras markedly inhibited phosphorylation of the C-terminal domain (CTD) of RNA polymerase II (pol II), known to regulate transcript elongation, accompanied by down-regulation of its principal kinase, cyclin-dependent kinase 7 (Cdk7). In contrast, nGAP elicited the opposite effects on each of these parameters. Furthermore, cotransfection of constitutively active Ras (12R Ras) with wild-type pol II, rather than a truncated mutant lacking the CTD, demonstrated that Ras activation of transcription was dependent on the pol II CTD. Consistent with a potential role for this pathway in the development of cardiac myocyte hypertrophy, alpha1-adrenergic stimulation similarly enhanced pol II phosphorylation and Cdk7 expression, where both effects were inhibited by dominant negative Ras, while pressure overload hypertrophy led to an increase in both hyperphosphorylated and hypophosphorylated pol II in addition to Cdk7.

Adenoviridae↗
PubMed1998

Chromosomal structural rearrangement of Paeonia brownii and P. californica revealed by fluorescence in situ hybridization.

Chromosomal structural rearrangement in Paeonia brownii and P. californica (2n = 10) was studied by in situ hybridization using 18S rDNA probes. Six major rDNA sites were detected in mitotic cells of P. californica; six major and two minor rDNA sites were found in P. brownii. Two cytotypes (A and B), with different chromosomal morphology and (or) rDNA locations, were observed in the population of P. californica. Cytotype A, with rDNA sites only on the short arms of chromosomes, was considered to be the normal cytotype. Both translocation and pericentric inversion may have occurred to give rise to cytotype B, in which one homolog of chromosome 4 has rDNA sites on both arms while its homolog has no rDNA sites: one homolog of chromosome 3 has a rDNA site on the long arm. Two rearranged cytotypes, C and D, were observed in the population of P. brownii. Given that the normal cytotype of P. brownii is most likely to have six major rDNA sites on the short arms of chromosomes 3, 4, and 5, and two minor sites on the short arms of chromosome 2, cytotype C may have resulted from a translocation between the short arm of one homolog of chromosome 2 and the long arm of one homolog of chromosome 4, and cytotype D may have resulted from a translocation between the short arm of one homolog of chromosome 3 and the long arm of one homolog of chromosome 4. These results supported previous observations, based on meiotic configurations, that chromosomal structural rearrangement occurred frequently in P. brownii and P. californica.

Chromosome Mapping↗