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Biomedical subjects

D Pan

Publications and source records attributed to D Pan.

At least 55 records · Page 3Linked to original sources
PubMed1996

KUZ, a conserved metalloprotease-disintegrin protein with two roles in Drosophila neurogenesis.

During neurogenesis in Drosophila both neurons and nonneuronal cells are produced from a population of initially equivalent cells. The kuzbanian (kuz) gene described here is essential for the partitioning of neural and nonneuronal cells during development of both the central and peripheral nervous systems in Drosophila. Mosaic analyses indicated that kuz is required for cells to receive signals inhibiting the neural fate. These analyses further revealed that the development of a neuron requires a kuz-mediated positive signal from neighboring cells. The kuz gene encodes a metalloprotease-disintegrin protein with a highly conserved bovine homolog, raising the possibility that kuz homologs may act in similar processes during mammalian neurogenesis.

Amino Acid Sequence↗
PubMed1996

Preclinical studies of lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II).

To explore the feasibility of ex vivo lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II), we evaluated retrovirus-mediated gene transfer of the iduronate-2-sulfatase (IDS) coding sequence into peripheral blood lymphocytes from enzyme-deficient individuals (PBLMPS). Moloney murine leukemia virus-derived retroviral vectors were constructed by inserting the IDS cDNA under transcriptional regulation of the long terminal repeat (LTR) (in vector L2SN) or the cytomegalovirus (CMV) early promoter (vector LNC2). High-titer virus-producer cells were generated using amphotropic PA317 packaging cells. After 3 days of in vitro stimulation of T lymphocytes with anti-CD3 antibody and interleukin-2 (IL-2), PBLMPS were transduced once on each of the next 3 days. Seven to 21 days later, cultured PBLMPS were evaluated for gene transfer and IDS specific activity. Heterogeneous populations of L2SN-transduced PBLMPS had high levels of IDS enzyme activity (456 U/mg per hr +/- SD 292) despite a gene transfer efficiency of 5% or less. Owing to overexpression of IDS in that percentage of PBLMPS successfully transduced, IDS activity was increased above the deficiency found in patients with Hunter syndrome (< 20 U/mg per hr) to a level comparable with that of normal individuals (mean activity of uncultured normal leukocytes 807 U/mg per hr; SD 252). Reduced 35SO4-glucosaminoglycan (GAG) accumulation was observed in PBLMPS that had been transduced with L2SN, or when PBLMPS were grown in medium that had been "conditioned" by growth of L2SN-transduced cells. This latter result indicated that metabolic cross-correction occurred by means of intercellular enzyme transfer. These studies of retrovirus-mediated expression and metabolic correction, finding near-normal levels of IDS in cultured PBLMPS and metabolic correction, demonstrate the potential for treatment of mild, nonneuropathic Hunter syndrome by means of ex vivo lymphocyte gene therapy.

Cytomegalovirus↗
PubMed1996

Affinities of methylphenidate derivatives for dopamine, norepinephrine and serotonin transporters.

We have synthesized several derivative of dl-threo-methylphenidate (Ritalin) bearing substituents on the phenyl ring. IC50 values for binding these compounds to rat brain monoamine transporters were assessed using [3H]WIN 35,428 (striatal membranes, dopamine transporters, DAT), [3H]nisoxetine (frontal cortex membranes, norepinephrine transporters, NET) and [3H]paroxetine (brain stem membranes, 5HT transporters, 5HTT). Affinities (1/Ki) decreased in the order: DAT > NET >> 5HTT. Substitution at the para position of dl-threo-methylphenidate generally led to retained or increased affinity for the dopamine transporter (bromo > iodo > methoxy > hydroxy). Substitution at the meta position also increased affinity for the DAT (m-bromo > methylphenidate; m-iodo-p-hydroxy > p-hydroxy). Substitution at the ortho position with bromine considerably decreased affinity. Similar IC50 values for binding of o-bromomethylphenidate to the dopamine transporter were measured at 0, 22 and 37 degrees. N-Methylation of the piperidine ring of methylphenidate also considerably reduced affinity. The dl-erythro isomer of o-bromomethylphenidate did not bind to the DAT (IC50 > 50,000 nM). Affinities at the dopamine and norepinephrine transporters for substituted methylphenidate derivatives were well correlated (r2=0.90). Abilities of several methylphenidate derivatives to inhibit [3H]dopamine uptake in striatal synaptosomes corresponded well with inhibition of [3H]WIN 35, 428 binding. None of the compounds examined exhibited significant affinity to dopamine D1 or D2 receptors (IC50 > 500 or 5,000 nM, respectively), as assessed by inhibition of binding of [3H]SCH 23390 or [123I]epidepride, respectively, to striatal membranes.

Animals↗
PubMed1996

Alcohol and preoperative management.

The French paradox is a recently coined term used to describe the lower incidence of heart disease in the French as compared with Americans in the face of increased cholesterol intake, higher serum cholesterol levels, and elevated blood pressures. The principal lifestyle factor explaining this paradox is alcohol intake. Research has shown that alcohol in general and wine in particular have myriad effects on the cardiovascular system--raising high-density lipoprotein levels, increasing antioxidant capabilities, and prolonging platelet aggregation. The most impressive benefits of alcohol appear to be platelet-related. Research has demonstrated an undeniable effect of alcohol on platelet function and bleeding characteristics. This information has been used recently to modify risk factors for heart disease; however, these data have a role in the preoperative management of surgical patients. In order to decrease the incidence and severity of intraoperative and postoperative bleeding, patients should be advised to abstain from alcohol and particularly red wine before surgery. In addition, alcohol has been found to have a synergistic effect with aspirin on bleeding times. These two substances, both individually and in combination, should be avoided preoperatively.

Animals↗
PubMed1996

Molecular genetic defect underlying alpha-L-iduronidase pseudodeficiency.

Mucopolysaccharidosis type I (i.e., Hurler, Hurler-Scheie, and Scheie syndromes) and type II (i.e., Hunter syndrome) are lysosomal storage disorders resulting from alpha-L-iduronidase (IDUA) deficiency and iduronate-2-sulfatase (IDS) deficiency, respectively. The a priori probability that both disorders would occur in a single individual is approximately 1 in 5 billion. Nevertheless, such a proband was referred for whom clinical findings (i.e., a male with characteristic facies, dysostosis multiplex, and mental retardation) and biochemical tests indicated these concomitant diagnoses. In repeated studies, leukocyte 4 methylumbelliferyl-alpha-L-iduronidase activities in this kindred were as follows: <1.0 nmol/mg protein/h in the proband and proband's clinically normal sister; 45.3 in mother; and 45.7 in father (normal range 65.0-140). Leukocyte L-O-(alpha-iduronate-2-sulfate)-(1->4)-D-O-2,5-anhydro[1-3H]mannitol-6- sulfate activities were as follows: 0.0 U/mg protein/h in the proband; 5.7 in his sister; 4.9 in mother; and 15.0 in father (normal range 11.0-18.4). Multiple techniques, including automated sequencing of the entire IDS and IDUA coding regions, were employed to unravel the molecular genetic basis of these intriguing observations. The common IDS mutation R468W was identified in the proband, his mother, and his sister, thus explaining their biochemical phenotypes. Additionally, the proband, his sister, and his father were found to be heterozygous for a common IDUA mutation, W402X. Notably, a new IDUA mutation A300T was also identified in the proband, his sister, and his mother, accounting for reduced IDUA activity in these individuals; the asymptomatic sister, whose cells demonstrated normal glycosaminoglycan metabolism, is thus a compound heterozygote for W402X and the new allele. This A300T mutation is the first IDUA pseudodeficiency gene to be elucidated at the molecular level.

Base Sequence↗
PubMed1996

[Studies on prematurely condensed chromosomes and induced condensed chromosomes with SEM].

The ultrastructure of prematurely condensed chromosomes (PCC) in BK cells and the CHO metaphase chromosomes (the PCC inducer) were studied with cell fusion technique and SEM. The methods for preparing complete specimens for SEM, were used to eliminate artifact as complete as possible, so the natural states of PCC ultrastructure, especially the ultrastructure of the early, mid, and late S-PCC, were observed for the first time. In the three phases of S-PCC multiple double strand helical structure were revealed, on the chromosome segments of BK cells. On the surface of CHO metaphase chromosomes which may induce PCC may regularly arrayed short hair-like loop-protrusions consisting of helical chromatin fibers were observed.

Animals↗
PubMed1996

[Replantation of 45 digits in 26 children: a long-term follow-up].

Twenty eight children with 47 amputated digits were replanted by the authors from 1978 to 1985. Among them 18 cases with 37 replanted digits was from 1 to 4 years old. The average age was 4.3 yrs. Forty six digits were salvaged, with survival rate of 97.8%. Twenty-six cases with 45 replanted digits have been examined from 9 to 15 years postoperatively. The follow-up rate was 92.8%. The hand functions assessed by criteriae of nakamura and tamai were excellent in 24 and good in 2 with out fair or poor grade. The two-point discrimination discrimination distance between 2-4 mm was 85%, The long term cosmetic appearance were good. The pulps of fingers were full and had rich blood supply. The satisfactory rate amounted to 96%. The excellent result obtained was due to strict adherence to the rules for replantation in childed cases: precise repair of all kinds of tissues and strict operative skill. The bone should be shortened less than 5 mm only. The follow-up X ray films taken from 9 to 15 years postoperatively showed the average shortening of the operated hand was 4 mm in comparison with the contralateral side. The lengths of the replanted phalanges were 3.8 mm shorter than the contralateral one. It means the absolute shortening during operation has no change while the lengths of the hand have some compensation in the process of growth. Those digits amputated at the interphalangeal joints had an average shortening of total hand length of 10.2 mm. Most joints were fused. The fact demonstrate that in joint amputation case the articular surface of proximal phalanx can be shortened while the distal articular joint surface should be preserved for preservation of epiphysis.

Amputation, Traumatic↗
PubMed1995

cAMP-dependent protein kinase and hedgehog act antagonistically in regulating decapentaplegic transcription in Drosophila imaginal discs.

Localized expression of decapentaplegic (dpp) is required for proper development of the Drosophila imaginal discs. Using genetic mosaics, we show that in the anterior compartment of appendage discs and anterior to the morphogenetic furrow in the eye disc, cells that lack cAMP-dependent protein kinase (PKA) activity ectopically express dpp. Pka- cells can influence the fate of neighboring cells to reorganize anterior patterns in appendages and trigger ectopic morphogenetic furrows in the developing retina. This organizing activity of Pka mutant cells depends on dpp activity. Our findings suggest that PKA is a component of a signaling pathway that represses dpp expression and that hh antagonizes this pathway to maintain dpp expression at the anterior-posterior compartment border and in the morphogenetic furrow.

Animals↗
PubMed1995

Tissue oxidative capacity, fuel stores and skeletal muscle fatty acid composition in obesity-prone and obesity-resistant rats.

The purpose of the present study was to compare tissue oxidative capacity, skeletal muscle fatty acid composition, and tissue fuel stores in low-fat fed (LFD, 12% of energy from corn oil) male Wistar rats, and in high-fat fed (45% of energy from corn oil) obesity-prone (OP) and obesity-resistant (OR) male Wistar rats. Designation of OP and OR rats was based on body weight gain (upper tertile for OP; lower tertile for OR) after 5 weeks on the high-fat diet. Body weight gain over the 5-week dietary period was 91 +/- 9 g in LFD, 98 +/- 4 g in OR, and 158 +/- 5 g in OP (p < 0.05 vs. LFD and OR). Energy intake over the 5-week dietary period was 3099 +/- 101 kcal in LFD, 3185 +/- 51 kcal in OR, and 3728 +/- 45 kcal in OP (p < 0.05 vs. LFD and OR). Maximal citrate synthase activity (mumol.g-1.min-1) in the gastrocnemius muscle was not significantly different among groups: 12.1 +/- 2.4 in LFD, 11.4 +/- 1.9 in OR and 13.3 +/- 2.5 in OP rats. Similarly, citrate synthase activity in the heart, 59.3 +/- 7.2, and liver, 6.6 +/- 0.4, was also not significantly different among groups. Fatty acid composition of the gastrocnemius muscle was not significantly different among groups. Fasting glycogen levels in the liver, gastrocnemius muscle, and heart were 6.4 +/- 3.7, 13.2 +/- 2.3 and 6.8 +/- 1.9 mumol/g in LFD, 21.2 +/- 5.1 (p < 0.05 vs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1995

Capacitation of mouse spermatozoa. I. Correlation between the capacitation state and protein tyrosine phosphorylation.

The molecular basis of mammalian sperm capacitation, defined functionally as those processes that confer on the sperm the acquisition of fertilization-competence either in vivo in the female reproductive tract or in vitro, is poorly understood. We demonstrate here that capacitation of caudal epididymal mouse sperm in vitro is accompanied by a time-dependent increase in the protein tyrosine phosphorylation of a subset of proteins of M(r) 40,000-120,000. Incubation of sperm in media devoid of bovine serum albumin, CaCl2 or NaHCO3, components which individually are required for capacitation, prevent the sperm from undergoing capacitation as assessed by the ability of the cells to acquire the pattern B chlortetracycline fluorescence, to undergo the zona pellucida-induced acrosome reaction and, in some cases, to fertilize metaphase II-arrested eggs in vitro. In each of these cases the protein tyrosine phosphorylation of the subset of capacitation-associated proteins does not occur. Protein tyrosine phosphorylation of these particular proteins, as well as sperm capacitation, can be recovered in media devoid of each of these three constituents (bovine serum albumin, CaCl2 or NaHCO3) by adding back the appropriate component in a concentration-dependent manner. The requirement of NaHCO3 for these phosphorylations is not due to an alkalinization of intracellular sperm pH or to an increase in media pH. Caput epididymal sperm, which lack the ability to undergo capacitation in vitro, do not display this capacitation-dependent subset of tyrosine phosphorylated proteins in complete media even after extended incubation periods, and do not fertilize metaphase II-arrested eggs in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Capacitation of mouse spermatozoa. II. Protein tyrosine phosphorylation and capacitation are regulated by a cAMP-dependent pathway.

In the accompanying report (Visconti, P.E., Bailey, J.L., Moore, G.D., Pan, D., Olds-Clarke, P. and Kopf, G.S. (1995) Development, 121, 1129-1137) we demonstrated that the tyrosine phosphorylation of a subset of mouse sperm proteins of M(r) 40,000-120,000 was correlated with the capacitation state of the sperm. The mechanism by which protein tyrosine phosphorylation is regulated in sperm during this process is the subject of this report. Cauda epididymal sperm, when incubated in media devoid of NaHCO3, CaCl2 or bovine serum albumin do not display the capacitation-associated increases in protein tyrosine phosphorylation of this subset of proteins. This NaHCO3, CaCl2 or bovine serum albumin requirement for protein tyrosine phosphorylation can be completely overcome by the addition of biologically active, but not inactive, cAMP analogues. Addition of the active cAMP analogues to sperm incubated in media devoid of NaHCO3, CaCl2 or bovine serum albumin overcomes the inability of these media to support capacitation, as assessed by the ability of the cells to acquire the pattern B chlortetracycline fluorescence, to undergo the zona pellucida-induced acrosome reaction and, in some cases, to fertilize metaphase II-arrested eggs in vitro. The effects of the cAMP analogues to enhance protein tyrosine phosphorylation and to promote capacitation appears to be at the level of the cAMP-dependent protein kinase (PKA), since two specific inhibitors of this enzyme (H-89 and Rp-cAMPS) block the capacitation-dependent increases in protein tyrosine phosphorylation in sperm incubated in media supporting capacitation. Capacitation, as assessed by the aforementioned endpoints, also appears to be inhibited by H-89 in a concentration-dependent manner. These results provide further evidence for the interrelationship between protein tyrosine phosphorylation and the appearance of the capacitated state in mouse sperm. They also demonstrate that both protein tyrosine phosphorylation and capacitation appear to be regulated by cAMP/PKA. Up-regulation of protein tyrosine phosphorylation by cAMP/PKA in sperm is, to our knowledge, the first demonstration of such an interrelationship between tyrosine kinase/phosphatase and PKA signaling pathways.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Binding of bromine-substituted analogs of methylphenidate to monoamine transporters.

We synthesized the o-, m- and p-bromo derivatives of dl-threo-methylphenidate from the corresponding bromophenylacetonitriles by modification of the literature synthesis of methylphenidate (Panizzon, Helv. Chim. Acta 1944, 27, 1748). In in vitro binding assays all three dl-threo bromo compounds had higher affinities than methylphenidate for dopamine transporter sites labeled with [3H]2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane ([3H]WIN 35,428; IC50 = 13, 4, 20 and 82 nM for o-, m-, and p-bromo compounds, and unsubstituted methylphenidate, respectively). They also bound more strongly than methylphenidate to norepinephrine reuptake sites labeled with [3H]nisoxetine (IC50 = 32, 20, 31 and 440 nM, respectively), but were weak ligands (IC50 > or = 1 microM) at the serotonin transporter labeled with [3H]paroxetine. In addition, the bromine substituted derivatives demonstrated similar activity to methylphenidate in vivo in rodents in terms of inhibition of heart uptake of [3H](-)-norepinephrine, elevation of striatal extracellular dopamine, and stimulation of locomotor activity.

Animals↗
PubMed1994

Gene trees and hominoid phylogeny.

Here we present a DNA sequence study that incorporates intraspecific variation from all five genera of hominoids (apes and humans). Recently it has been claimed that using single individuals to analyze species' relationships might be misleading if within-species variation is great. Our results indicate that despite high intraspecific variation in mitochondrial cytochrome oxidase subunit II gene sequences of some hominoids, humans and chimpanzees are nonetheless significantly most closely related. We also report the observation that variation within the gorilla species exceeds that between common and pygmy chimpanzee species, a finding with implications for conservation. In contrast, humans are less mitochondrially diverse than lowland gorillas inhabiting western Africa.

Animals↗
PubMed1994

The bipartite D. melanogaster twist promoter is reorganized in D. virilis.

The pivotal role of twist in mesoderm determination in the Drosophila embryo depends upon two processes--the transcriptional activation of twist in the ventrally located mesodermal anlage and the regulation of downstream gene expression by the twist transcription factor. To elucidate the molecular mechanisms involved in these processes, we have compared both the coding and regulatory regions of the twist genes from Drosophila melanogaster and Drosophila virilis. Within the coding region, the basic-helix-loop-helix DNA binding and dimerization motif is highly conserved, consistent with the functional importance of this domain. A comparison of the transcriptional regulatory regions reveals a high degree of conservation in the more distal of the two ventral activator regions that have been mapped in the twist 5' flanking region. On the other hand, the more proximal ventral activator region is absent at the corresponding position in the D. virilis twist gene. Instead, there is a region in the second intron of the D. virilis gene that resembles the proximal element of the D. melanogaster gene, in that it consists of little more than a series of whole and half binding sites for the dorsal morphogen. In transformation experiments, the intronic D. virilis element directs an expression pattern that is indistinguishable from that directed by the D. melanogaster proximal VAR. Thus, the twi genes from these two species appear to have evolved enhancer elements with very similar structural and functional properties. These findings suggest that apparently redundant spatially regulated enhancer elements may each play essential roles in fine tuning the level and/or pattern of gene expression.

Amino Acid Sequence↗
PubMed1994

Evidence that the major membrane lipids, except cholesterol, are made in axons of cultured rat sympathetic neurons.

Membrane lipids and proteins required for axonal growth and regeneration are generally believed to be synthesized in the cell bodies of neurons and transported into the axons. However, we have demonstrated recently that, in cultured rat sympathetic neurons, axons themselves have the capacity to synthesize phosphatidylcholine, sphingomyelin, and phosphatidylethanolamine. In these experiments, we employed a compartment model of neuron culture in which pure axons grow in a fluid environment separate from that containing the cell bodies. In the present study, we again used compartmented cultures to confirm and extend the previous results. We have shown that three enzymes of phosphatidylcholine biosynthesis via the CDP-choline pathway are present in axons. We have also shown that the rate-limiting step in the biosynthesis of phosphatidylcholine by this route in neurons, and locally in axons, is catalyzed by the enzyme CTP:phosphocholine cytidylytransferase. The biosynthesis of other membrane lipids, such as phosphatidylserine, phosphatidylethanolamine derived by decarboxylation of phosphatidylserine, phosphatidylinositol, and fatty acids, also occurs in axons. However, the methylation pathway for the conversion of phosphatidylethanolamine into phosphatidylcholine appears to be a quantitatively insignificant route for phosphatidylcholine synthesis in neurons. Moreover, our data provided no evidence for the biosynthesis of another important membrane lipid, cholesterol, in axons.

Acetates↗
PubMed1993

6q deletions define distinct clinico-pathologic subsets of non-Hodgkin's lymphoma.

Commonly observed in lymphoid neoplasms, deletions of 6q have been correlated with histologic and clinical subsets of non-Hodgkin's lymphoma (NHL). Our recent analysis of loss of heterozygosity of 6q loci in NHL showed two regions of minimal molecular deletion (RMD), an RMD1 at 6q25-27 and an RMD2 at 6q21-23. To establish correlations between these RMDs and regions of minimal cytogenetic deletions (RCDs) on 6q, and to define associations between RCDs and clinico-pathologic features, we have analyzed chromosome 6 abnormalities in 459 consecutively ascertained, karyotypically abnormal cases of NHL. Among these, 126 (27.5%) cases had structural abnormalities of chromosome 6, of which 94 were deletions. Analysis of these deletions identified three RCDs. An RCD1 encompassing 6q25-27 was seen in 45 intermediate-grade NHL. An RCD2 at 6q21 was observed in 11 high-grade NHL, 9 of which were of the immunoblastic subtype. An RCD3 at 6q23 was noted in 18 low-grade NHL lacking a t(14;18) translocation. Of these 18 cases, 12 were small lymphocytic NHL and, in 2 of these, del(6q) was the sole karyotypic abnormality. In 20 cases of low-grade NHL with t(14;18), the deletions spanned both RCD1 and RCD3. These data suggested the presence of at least 3 tumor suppressor genes on 6q within RCD1, RCD2, and RCD3; they also showed associations between RCDs in 6q and subsets of NHL, including a specific association between a group of well-differentiated lymphoid neoplasms and RCD3. The apparent heterogeneity of breakpoints when all NHLs are considered together explains the inability of previous studies to reliably establish correlations between recurring 6q deletions and histologic and clinical features of NHL.

Biopsy↗
PubMed1993

Mitochondrial COII sequences and modern human origins.

The aim of this study is to measure human mitochondrial sequence variability in the relatively slowly evolving mitochondrial gene cytochrome oxidase subunit II (COII) and to estimate when the human common ancestral mitochondrial type existed. New COII gene sequences were determined for five humans (Homo sapiens), including some of the most mitochondrially divergent humans known; for two pygmy chimpanzees (Pan paniscus); and for a common chimpanzee (P. troglodytes). COII sequences were analyzed with those from another relatively slowly evolving mitochondrial region (ND4-5). From class 1 (third codon position) sequence data, a relative divergence date for the human mitochondrial ancestor is estimated as 1/27 th of the human-chimpanzee divergence time. If it is assumed that humans and chimpanzees diverged 6 Mya, this places a human mitochondrial ancestor at 222,000 years, significantly different from 1 Myr (the presumed time of an H. erectus emergence from Africa). The mean coalescent time estimated from all 1,580 sites of combined mitochondrial data, when a 6-Mya human-chimpanzee divergence is assumed, is 298,000 years, with 95% confidence interval of 129,000-536,000 years. Neither estimate is compatible with a 1-Myr-old human mitochondrial ancestor. The mitochondrial DNA sequence data from COII and ND4-5 regions therefore do not support this multiregional hypothesis for the emergence of modern humans.

Animals↗