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J P Rossiter

Publications and source records attributed to J P Rossiter.

At least 19 recordsLinked to original sources
PubMed1998

Immunolabelling of the cytoplasm and processes of apoptotic facial motoneurons following axotomy in the neonatal rat.

A polyclonal antibody intended to recognize c-Jun (Oncogene Science, c-jun/AP-1, Ab-2) has previously been shown to recognize an apparently novel "apoptosis-specific protein" (ASP) in the cytoplasm of cells undergoing apoptotic cell death in vitro. We have investigated whether this antibody would also serve as a reliable marker for apoptotic motoneurons in vivo. Following transection of the left facial nerve in anesthetized neonatal rat pups, which results in over 90% death of the facial motoneurons, we performed immunohistochemistry on frozen brain stem sections with Oncogene Science Ab-1 and Ab-2 antibodies which are raised against different peptide fragments of c-Jun. While Ab-1/c-Jun labelling was seen in the nuclei of the majority of axotomized motoneurons, Ab-2/ASP immunoreactivity was present only in scattered cells, all of which had characteristic apoptotic morphology. Furthermore, Ab-2/ASP immunoreactivity was cytoplasmic and frequently included the dendrites and axons of dying neurons. Some cerebellar granule cells undergoing postnatal developmental cell death were also Ab-2/ASP positive. The time course of the number of Ab-2/ASP-labelled motoneurons corresponded relatively closely with our previous data on DNA fragmentation in these cells, as assessed by an in situ end labelling (ISEL) technique. When facial nerve axotomy was performed at 7 and 14 days postnatum, resulting in reduced cell death, the number of Ab-2/ASP immunoreactive cells decreased correspondingly. Although the exact identity of the epitope recognized by Ab-2 is unclear, we conclude that, by labelling the cytoplasmic and neuritic components of apoptotic motoneurons, Ab-2/ASP immunohistochemistry is a valuable complementary technique to existing in situ methods based on the detection of fragmented DNA in the cell nucleus.

Animals↗
PubMed1997

Apoptotic cell death is an important cause of neuronal injury in experimental Venezuelan equine encephalitis virus infection of mice.

Mice develop a fatal encephalomyelitis after infection with the Trinidad donkey strain of Venezuelan equine encephalitis (VEE) virus. Adult mice were inoculated intraperitoneally with VEE virus and the brains were examined at different time points. Morphological changes were assessed by histological staining. VEE virus antigen was detected with immunoperoxidase staining, and DNA fragmentation was evaluated in situ using the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) method. VEE antigen was found in many areas of the brain and it was prominent in neurons. There were mild associated inflammatory changes. DNA fragmentation was demonstrated in many of these areas using TUNEL. In areas with TUNEL staining, morphological neuronal changes ranged from nuclear chromatin condensations to nuclear and cellular fragmentation, which are characteristic of apoptosis. There is strong morphological and biochemical evidence of apoptotic cell death in this experimental model of VEE virus infection.

Animals↗
PubMed1997

Apoptosis plays an important role in experimental rabies virus infection.

Cultured rat prostatic adenocarcinoma (AT3) cells infected with the challenge virus standard (CVS) strain of fixed rabies virus showed characteristic morphologic features of apoptosis, evidence of oligonucleosomal DNA fragmentation, and expression of the Bax protein. CVS-infected Bcl-2-transfected AT3 cells did not demonstrate these features. Adult ICR mice inoculated intracerebrally with CVS showed morphologic changes of apoptosis, DNA fragmentation, and increased Bax expression in neurons, with changes most marked in the hippocampus and cerebral cortex. Ultrastructurally, some neurons demonstrated morphologic features more typical of necrosis. These studies provide evidence that apoptosis plays an important role in the pathogenesis of rabies virus infection.

Animals↗
PubMed1996

Axotomy-induced apoptotic cell death of neonatal rat facial motoneurons: time course analysis and relation to NADPH-diaphorase activity.

Rapid and massive death of motoneurons occurs following axotomy in neonatal mammals. This likely results from the neurons being deprived of access to target-derived trophic factors, as their death can be prevented by application of a variety of neurotrophic factors to the proximal end of the cut nerve. Since trophic factor-deprived embryonic chick motoneurons undergo apoptosis in vitro, we have investigated whether axotomized neonatal rat facial motoneurons undergo apoptotic cell death in vivo. Following facial nerve transection during the first postnatal day, the dying motoneurons show characteristic morphological changes of apoptosis and undergo DNA fragmentation, as detected by an in situ end labeling technique. An initial sharp burst of DNA fragmentation, between 12 and 24 h postaxotomy, accompanies a steep decline in neuronal numbers, indicating that neuronal cell death rapidly follows endonuclease cleavage of DNA. However, the interval between axotomy and onset of DNA fragmentation varies widely. By 4 days postnatum only 38% of the lesioned motoneurons have survived an initial rapid phase of neuronal loss, whereas 11% survive to 10 days postnatum at least. NADPH-diaphorase/nitric oxide synthase activity has been implicated as having a causal role in the death of lesioned motoneurons. We have found that there is a sustained increase in the intensity of NADPH-diaphorase histochemical staining in axotomized neonatal facial motoneurons, but that this is first detectable well after the onset of DNA fragmentation and cell death. This suggests that nitric oxide, or its metabolites, does not initiate cell death in this model.

Animals↗
PubMed1995

Factor VIII gene inversions in severe hemophilia A: results of an international consortium study.

Twenty-two molecular diagnostic laboratories from 14 countries participated in a consortium study to estimate the impact of Factor VIII gene inversions in severe hemophilia A. A total of 2,093 patients with severe hemophilia A were studied; of those, 740 (35%) had a type 1 (distal) factor VIII inversion, and 140 (7%) showed a type 2 (proximal) inversion. In 25 cases, the molecular analysis showed additional abnormal or polymorphic patterns. Ninety-eight percent of 532 mothers of patients with inversions were carriers of the abnormal factor VIII gene; when only mothers of nonfamilial cases were studied, 9 de novo inversions in maternal germ cells were observed among 225 cases (approximately 1 de novo maternal origin of the inversion in 25 mothers of sporadic cases). When the maternal grandparental origin was examined, the inversions occurred de novo in male germ cells in 69 cases and female germ cells in 1 case. The presence of factor VIII inversions is not a major predisposing factor for the development of factor VIII inhibitors; however, slightly more patients with severe hemophilia A and factor VIII inversions develop inhibitors (130 of 642 [20%]) than patients with severe hemophilia A without inversions (131 of 821 [16%]).

Blotting, Southern↗
PubMed1995

Smith-Lemli-Opitz syndrome: prenatal diagnosis by quantification of cholesterol precursors in amniotic fluid.

Until recently, the diagnosis of Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive malformation/mental retardation syndrome, was made on the basis of clinical criteria alone. As a result, prenatal diagnosis has been possible only if sonography disclosed distinct fetal malformations in a subsequent pregnancy. However, the recent description of increased levels of 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol) in patients with SLOS, most likely caused by a deficiency of 3 beta-hydroxysteroid-delta 7-reductase, has provided an apparently reliable biochemical marker for diagnosis of SLOS. To determine if this abnormality of sterol metabolism has utility for prenatal diagnosis of SLOS, we measured the levels of neutral sterols in stored amniotic fluid samples from two SLOS pregnancies. In both cases, the diagnosis of SLOS was made in the neonatal period by clinical criteria and the finding of markedly increased levels of 7-dehydrocholesterol in plasma. Quantitative analysis by gas chromatography of sterols extracted from the amniotic fluid of both pregnancies revealed similar, markedly increased levels of 7-dehydrocholesterol and its precursor, lathosterol (cholest-7-en-3 beta-ol), both of which were undetectable in reference amniotic fluids. These findings suggest that abnormalities of cholesterol biosynthesis in SLOS may be sufficiently expressed in fetal life to permit prenatal diagnosis of this disorder by measurement of 7-dehydrocholesterol in amniotic fluid.

Amniotic Fluid↗
PubMed1995

A prospective longitudinal evaluation of pregnancy in the Marfan syndrome.

OBJECTIVE: We undertook a prospective evaluation of the outcomes of pregnancy, both maternal and fetal, and the long-term impact of pregnancy on Marfan syndrome in a series of consecutive, unselected patients. STUDY DESIGN: Forty-five pregnancies in 21 Marfan syndrome patients were prospectively observed in one institution between 1983 and 1992. During pregnancy, patients were monitored with serial echocardiograms and close attention to symptoms. Maternal and fetal outcomes were monitored with serial echocardiographic data were analyzed by least-squares regression. Eighteen of the patients were followed up for 15 months to 13 years after the completion of their last pregnancy for investigation of the long-term impact of pregnancy on the cardiovascular manifestations of Marfan syndrome. RESULTS: Aortic dissection occurred in two patients, both with increased risk for dissection established before pregnancy. The incidence of obstetric complications otherwise did not exceed that in the general population. Echocardiographic data demonstrated little to no change in aortic root diameter throughout pregnancy in most patients. Long-term follow-up showed no apparent worsening of cardiovascular status attributable to pregnancy in comparison with a group of 18 women with Marfan syndrome who were of similar age, had a similar degree of disease severity, and underwent no pregnancies. CONCLUSIONS: Patients with Marfan syndrome in whom cardiovascular involvement is minor and aortic root diameter is < 40 mm usually tolerate pregnancy well, with favorable maternal and fetal outcomes, and without subsequent evidence of aggravated aortic root dilatation over time.

Abortion, Spontaneous↗
PubMed1994

The use of polymerase chain reaction to determine fetal RhD status.

OBJECTIVE: Our purpose was (1) to establish the accuracy of a deoxyribonucleic acid amplification method in determination of RhD status in adult blood samples, including weak D variants (previously referred to as Du) and a D mosaic, and (2) to apply the method to determine fetal RhD status in alloimmunized pregnancies. STUDY DESIGN: Twenty-five adult blood samples, including five weak D variants and one D mosaic, were analyzed with a polymerase chain reaction to determine RhD type. The method was then applied to amniotic fluid samples obtained by amniocentesis from three RhD-negative women with known RhD sensitization. RESULTS: RhD type determined by polymerase chain reaction for all adult blood samples agreed with serologic typing results. All weak D variants and the D mosaic gave results consistent with RhD positivity. Fetal RhD status was determined in each of the three alloimmunized pregnancies, and obstetric management decisions were made on the basis of these results. CONCLUSIONS: This polymerase chain reaction method allows rapid and accurate determinations of fetal RhD status by amniocentesis. Fetal blood sampling or serial amniocenteses may be avoided when the fetus is RhD negative, and plans for surveillance and intervention can be confidently made if the fetus is RhD positive. However, before the widespread use of this assay, its sensitivity and specificity must be established. Because weak D variants and a D mosaic demonstrated RhD-positive status by polymerase chain reaction, the method described is applicable to these RhD variants.

Adult↗
PubMed1994

Factor VIII gene inversions causing severe hemophilia A originate almost exclusively in male germ cells.

The factor VIII gene, which is defective in hemophilia A, is located in the last megabase of the long arm of the X chromosome. Inversions due to intrachromosomal homologous recombination between mispaired copies of gene A located within intron 22 of the gene and about 500 kb telomeric to it account for nearly half of all cases of severe hemophilia A. We hypothesized that pairing of Xq with its homolog inhibits the inversion process, and that, therefore, the event originates predominantly in male germ cells. In all 20 informative cases in which the inversion originated in a maternal grandparent, DNA polymorphism analysis determined that it occurred in the male germline. In addition, all but one of 50 mothers of sporadic cases due to an inversion were carriers. Thus, these data support the hypothesis and indicate that factor VIII gene inversions leading to severe hemophilia A occur almost exclusively in male germ cells.

Blotting, Southern↗
PubMed1993

Prenatal diagnosis of congenital heart disease.

In counseling the patient with a fetus with CHD, attempts should be made to determine the exact cardiac diagnosis and whether there are associated extracardiac or chromosomal abnormalities. A careful family history and examination of appropriate family members may lead to the diagnosis of a genetic syndrome. An evaluation of the maternal medical and obstetric history will explore the possibility of maternal disease states, teratogens, or environmental exposures as cause for the cardiac lesion. The information obtained from a prenatal evaluation may lead to a possible cause of CHD in the fetus and thus more accurate counseling regarding recurrence risks and the prognosis for the present pregnancy. With further improvement in the prenatal diagnosis of structural cardiac disease, a knowledge of possible causes is essential for the clinician providing counseling. In addition, a multidisciplinary approach with the involvement of obstetricians, neonatologists, pediatric cardiologists, cardiac surgeons, and geneticists will optimize care in pregnancies complicated by a fetus with structural heart disease.

Echocardiography↗
PubMed1992

Management of genetic disorders during pregnancy.

Using several specific genetic diseases as examples, this article has illustrated basic genetic principles that can be applied to many clinical situations. Practicing obstetricians must be aware that advances are being made daily in the care of patients with inherited disorders and in prenatal diagnosis. A fundamental understanding of human genetics is essential in order to offer optimal care for patients during their reproductive years.

Cystic Fibrosis↗
PubMed1991

Myelin-axon relationships established by rat vagal Schwann cells deep to the brainstem surface.

The central-peripheral transitional zones of rat dorsolateral vagal rootlets are highly complex. Peripheral nervous tissue extends centrally for up to several hundred micrometers deep to the brainstem surface along these rootlets. In some instances this peripheral nervous tissue lacks continuity with the peripheral nervous system (PNS) and so forms an island within the central nervous system (CNS). In conformity with the resulting complexity of the CNS-PNS interface, segments of vagal axons lying deep to the brainstem surface are myelinated by one or more intercalated Schwann cells, contained in peripheral tissue insertions or islands, at either end of which they traverse an astroglial barrier. Intercalated Schwann cells are thus isolated from contact or contiguity with the Schwann cells of the PNS generally. They are short, having a mean internodal length of around 60% of that of the most proximal Schwann cells of the PNS proper, which lie immediately distal to the CNS-PNS interface and which are termed transitional Schwann cells. The thickness of the myelin sheaths produced by intercalated Schwann cells is intermediate between that of transitional Schwann cells and that of oligodendrocytes myelinating vagal axons of the same calibre distribution. This is not due to limited blood supply or to insufficient numbers of intercalated Schwann cells, the density of which is greater than that of transitional Schwann cells. These factors are unlikely to restrict expression of their myelinogenic potential. Nevertheless, the regression data show that the setting of the myelin-axon relationship differs significantly between the two categories of Schwann cell. Thus, the myelinogenic response of Schwann cells to stimuli emanating from the same axons may differ between levels along one and the same nerve bundle. Mean myelin periodicity was found to differ between sheaths produced by intercalated and by transitional Schwann cells.

Animals↗
PubMed1990

Intermingling of central and peripheral nervous tissues in rat dorsolateral vagal rootlet transitional zones.

The morphology of the CNS-PNS transitional zone of adult rat dorsolateral vagus nerve rootlets is uniquely complex. A typical rootlet contains a transitional zone over 300 microns long, consisting of a central tissue projection extending distally into each rootlet and a peripheral tissue insertion extending for a longer distance deep into the brainstem. The peripheral tissue insertion is continuous with the peripheral tissue of the free rootlet through channels traversing or running parallel to the central tissue projection. Accordingly, the vagal CNS-PNS interface is topologically much more complex than that found elsewhere. In some rootlets the peripheral tissue in the brainstem constitutes an isolated island deep within the neuraxis. In others, peripheral continuity is established only through a cross connection with the peripheral tissue insertion of a neighbouring rootlet. About one fifth of all vagal myelinated axons alternate between the CNS and PNS tissue compartments. This distinguishes the vagus from all other nerves studied to date. These axons are myelinated by Schwann cells distal to the transitional zone, by oligodendrocytes in the central tissue projection and by one or more short intercalated Schwann internodes further centrally, mostly in the peripheral tissue insertion, where their perikarya commonly form closely apposed aggregates. More than four fifths of all unmyelinated axon bundles alternate between central and peripheral tissue compartments, commonly more than once. In the peripheral tissue insertion axons are enveloped by series of non-myelinating Schwann cells. Schwann processes commonly extend for over 50 microns into the central compartment at each central-peripheral transition. Around one fifth of peripherally unmyelinated axons have an oligodendrocytic sheath in the central compartment. Of these axons possessing more than one intercalated Schwann internode, over one quarter display alternation of myelinated and unmyelinated segments in the peripheral tissue insertion. Astrocytes in the transitional zone segregate PNS tissue, a role played by sheath cells further peripherally in the vagal rootlets. Astrocytes form the surface limiting membranes of the central tissue projection and the barrier between the peripheral tissue insertion and the surrounding brainstem. The barrier consists only of an attenuated layer of processes. This is deficient in places, where oligodendrocytic myelin sheaths are directly exposed to the endoneurial space of the peripheral tissue insertion and in some instances are apposed to myelinating or non-myelinating Schwann cells. Such communication between the central and peripheral compartments is unique to the vagal transitional zone. The findings are consistent with a range of possible events during development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Origin of the human L1 elements: proposed progenitor genes deduced from a consensus DNA sequence.

A consensus sequence for the human long interspersed repeated DNA element, L1Hs (LINE or KpnI sequence), is presented. The sequence contains two open reading frames (ORFs) which are homologous to ORFs in corresponding regions of L1 elements in other species. The L1Hs ORFs are separated by a small evolutionarily nonconserved region. The 5' end of the consensus contains frequent terminators in all three reading frames and has a relatively high GC content with numerous stretches of weak homology with AluI repeats. The 5' ORF extends for a minimum of 723 bp (241 codons). The 3' ORF is 3843 bp (1281 codons) and predicts a protein of 149 kD which has regions of weak homology to the polymerase domain of various reverse transcriptases. The 3' end of the consensus has a 208-bp nonconserved region followed by an adenine-rich end. The organization of the L1Hs consensus sequence resembles the structure of eukaryotic mRNAs except for the noncoding region between ORFs. However, due to base substitutions or truncation most elements appear incapable of producing mRNA that can be translated. Our observation that individual elements cluster into subfamilies on the basis of the presence or absence of blocks of sequence, or by the linkage of alternative bases at multiple positions, suggests that most L1 sequences were derived from a small number of structural genes. An estimate of the mammalian L1 substitution rate was derived and used to predict the age of individual human elements. From this it follows that the majority of human L1 sequences have been generated within the last 30 million years. The human elements studied here differ from each other, yet overall the L1Hs sequences demonstrate a pattern of species-specificity when compared to the L1 families of other mammals. Possible mechanisms that may account for the origin and evolution of the L1 family are discussed. These include pseudogene formation (retroposition), transposition, gene conversion, and RNA recombination.

Biological Evolution↗
PubMed1987

Maternal serum alpha-fetoprotein screening after chorionic villus sampling.

To evaluate whether maternal serum alpha-fetoprotein (MSAFP) concentrations at 15-18 weeks' gestation are influenced by chorionic villus sampling performed three to ten weeks earlier, MSAFP levels were determined for 417 postchorionic villus sampling patients and 967 control subjects without previous chorionic villus sampling. Statistical comparison of the medians, distributions, and proportions above defined multiples of the median demonstrated no significant difference between the two populations. These results indicate that MSAFP screening in postchorionic villus sampling patients should be reliable and that values may be interpreted using criteria similar to those used for the general population.

Adult↗
PubMed1983

Cell clusters on rat ventral roots: postnatal development.

The cell clusters found on the most proximal parts of rat ventral spinal nerve rootlets during prenatal development, persist into the postnatal period. Clusters become smaller as cells leave them to invest axon segments. By 2 weeks after birth, clusters have largely disappeared. Fine processes stemming from clusters interweave at first to envelop axons in a complex matrix. This matrix disappears soon after birth. Axons then become enveloped by cells in clusters in the manner of premyelin Schwann cells. Many of these premyelin cells leave the parent cluster but continue to envelop the unmyelinated axon segment as they do so. Meanwhile, myelination of axons immediately distal to the proximal rootlet segment proceeds at the same rate as in the ventral root generally. Thus, the proximodistal maturation gradient comes to be reversed in relation to many axons in the ventral root, the most proximal peripheral internode being unmyelinated, while more distal internodes are myelinated. This reversal gradually lessens in some cases as the short internodes produce myelin sheaths. It is possible that these short internodes become progressively more heavily myelinated and elongate in subsequent development. All axons in the most proximal part of the ventral rootlet do not necessarily become enveloped by short premyelin Schwann cells, however. When some are released from envelopment by the matrix, the myelinating Schwann cells at more distal root levels extend proximally along each of them, up to the level of the surface of the spinal cord. Some clusters in the early postnatal period contain cells resembling astrocytes.

Animals↗