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A Corbett

Publications and source records attributed to A Corbett.

At least 19 recordsLinked to original sources
PubMed2000

CNS voltage-dependent Na(+) channel expression and distribution in an undifferentiated and differentiated CNS cell line.

Upon serum removal, CAD-R1 cells undergo neurite outgrowth and an increase in voltage-dependent Na(+) current (VDNaC) density without changing their activation and inactivation properties. Insulin and endothelial cell growth supplement inhibited the increase in VDNaC density but not the neurite outgrowth. RI, RII, RIII Na(+) channel proteins were expressed in CAD-R1 cells. These proteins exhibited both similar and different distribution and clustering patterns which suggested the channel's structural differences play a role in channel distribution.

Cell Culture Techniques↗
PubMed1998

Efficient neurophysiologic selection of X-linked Charcot-Marie-Tooth families: ten novel mutations.

OBJECTIVE: To devise a neurophysiologic strategy to select X-linked Charcot-Marie-Tooth neuropathy syndrome (CMTX) families for connexin 32 mutation screening. BACKGROUND: Once the common chromosome 17 DNA duplication (CMT1A syndrome) has been excluded, clinical features are not sufficiently distinctive to select which of three genes (PMP22, Po, or connexin 32) should be screened for mutations. DESIGN: The yield of connexin 32 mutations was compared in possible CMTX families with clinical and genetic features of CMTX and probable CMTX families, defined by additional characteristic neurophysiologic features of CMTX. Of 232 CMT families with median motor nerve conduction velocities below 50 m/second (s) in affected men, 50 were found to have no CMT1A duplication and a pattern of inheritance compatible with CMTX (no man-to-man inheritance of CMT). These families were divided into 23 probable CMTX families (defined as having electrophysiologic indicators of CMTX), 23 possible CMTX families (with no neurophysiologic features of CMTX), and five unlikely CMTX families (with normal brainstem evoked auditory potentials [BAEPs]). RESULTS: The yield of mutations in the whole group was 25 mutations in 51 families (50%). Most probable CMTX families (21 of 23; 91%) had connexin 32 coding region mutations. Included in this group were 14 families with obligate female carriers; 11 of these had intermediate conduction velocities (>42 m/s) and nine (81%) had connexin 32 mutations. Only 3 of 23 (13%) possible CMTX families had connexin 32 mutations. One of five families with normal BAEPs in affected men had a connexin 32 mutation, and one had a Po Ala112Val mutation. Seventeen different mutations were found among 24 families, including 10 previously undescribed mutations (Leu9Trp, Ile28Thr, Ile30Thr, Ile127Met, Leu131Pro, Tyr154 stop, Pro158Ala, one base deletion of codon 158 causing stop at codon 195, Val192Phe, and Leu239Ile). CONCLUSIONS: The yield of connexin 32 mutations can be increased from approximately 6% of all CMT type I families to 91% of nonduplicated nondominant families with characteristic electrophysiologic changes of CMTX.

Amino Acid Substitution↗
PubMed1997

Sex differences and the development of social behavior in a marsupial, the gray short-tailed opossum (Monodelphis domestica).

The effects of sex and age on social behavior were examined in gray short-tailed opossums (Monodelphis domestica), small didelphid marsupials. Each animal received five behavior test batteries spanning prepubertal to postpubertal ages. Each test battery consisted of two tests with animals of the same age, one with a male and one with a female. Precopulatory behavior toward females, intermale fighting requiring test interruptions as well as scent marking behavior were seen at higher levels in males than in females and were seen more frequently around and after puberty than before puberty. Females showed more threat behavior than males in mixed-sex and in same-sex interactions. This sex difference was apparent after puberty in tests with male partners and prior to as well as around puberty in tests with female partners. Because climbing over and boxing with another animal were seen more frequently prior to than after puberty, these behaviors may be elements of play fighting (i.e. attack and defense without submission and threat). These findings are discussed with respect to the role of gonadal hormones in the organization and activation of behavior and with reference to their comparative significance in mammals.

Age Factors↗
PubMed1996

Genetic analysis of macromolecular transport across the nuclear envelope.

Numerous factors that promote movement of macromolecules in and out of the nucleus have now been identified. These include both soluble cytoplasmic and nucleoplasmic proteins and proteins of the nuclear pore complex (NPC). Genetic analyses of the nuclear transport process in the model organism, the budding yeast Saccharomyces cerevisiae, have revealed remarkable conservation of all of these factors. In addition, important clues as to how these factors promote the unique bidirectional movement across the NPC have emerged from studies of yeast. We summarize the characterization and genetic interactions of the soluble transport factors and present data to illustrate how genetic experiments can be used to further define the import and export pathways.

Biological Transport, Active↗
PubMed1996

A double-blind comparison of 0.25% ropivacaine and 0.25% bupivacaine for extradural analgesia in labour.

Ropivacaine is a new aminoamide local anaesthetic. Compared with bupivacaine, ropivacaine possesses a higher threshold for systemic toxicity and a high selectivity for sensory fibres. We have compared prospectively these two agents in a concentration of 0.25% for extradural analgesia in labour. A total of 104 parturients requesting extradural analgesia were randomized to receive either ropivacaine or bupivacaine. The women in the bupivacaine group required more top-up doses to maintain analgesia (median 3.0 vs 2.0) (P < 0.05). The onset of sensory block, quality of analgesia, ultimate level of maximum sensory block and maternal satisfaction were similar in both groups. The incidence, intensity and duration of motor block were slightly but not significantly less in the ropivacaine group. The ropivacaine group had a higher incidence of spontaneous vaginal delivery (70.59% vs 52.00%). There was no significant difference in neonatal outcome as assessed by Apgar scores, umbilical acid-base status and neurological and adaptive capacity score at 2 and 24 h after delivery. We conclude that ropivacaine and bupivacaine in a concentration of 0.25% produced comparable analgesia for pain relief of labour with no detectable adverse effect on the neonate.

Adolescent↗
PubMed1996

SEC3 mutations are synthetically lethal with profilin mutations and cause defects in diploid-specific bud-site selection.

Replacement of the wild-type yeast profilin gene (PFY1) with a mutated form (pfy1-111) that has codon 72 changed to encode glutamate rather than arginine results in defects similar to, but less severe than, those that result from complete deletion of the profilin gene. We have used a colony color-sectoring assay to identify mutations that cause pfy1-111, but not wild-type, cells to be inviable. These profilin synthetic lethal (psl) mutations result in various degrees of abnormal growth, morphology, and temperature sensitivity in PFY1 cells. We have examined psl1 strains in the most detail. Interestingly, these strains display a diploid-specific defect in bud-site selection; haploid strains bud normally, while homozygous diploid strains show a dramatic increase in random budding. We discovered that PSL1 is the late secretory gene, SEC3, and have found that mutations in several other late secretory genes are also synthetically lethal with pfy1-111. Our results are likely to reflect an interdependence between the actin cytoskeleton and secretory processes in directing cell polarity and growth. Moreover, they indicate that the secretory pathway is especially crucial for maintaining budding polarity in diploids.

Actins↗
PubMed1996

Slowing of central conduction in X-linked Charcot-Marie-Tooth neuropathy shown by brain stem auditory evoked responses.

BACKGROUND: The most common form of CMT with slow nerve conduction velocities (CMT type I) is CMT1A, caused by a submicroscopic duplication of a region of DNA on chromosome 17 including the PMP22 gene. This gene is expressed in peripheral nerve but not in the CNS. The second most common form is CMTX, caused by mutations in the connexin32 gene in the X chromosome. Connexin32 is expressed both in brain and in peripheral nerve. These molecular variants are difficult to distinguish clinically. METHODS: Brain stem auditory evoked responses (BAERs) were measured in patients with CTMX and CMT1A. RESULTS: BAERs showed central conduction slowing in male patients with CMTX which did not overlap the normal range. Patients with CMT1A had a delay in wave I latency but otherwise normal responses. These results are consistent with the pattern of expression of PMP22 in the peripheral portion of the eighth nerve (myelinated by Schwann cells) and of connexin32 in the central portion in the brainstem auditory pathways (myelinated by oligodendrocytes). This is the first evidence for central involvement in CMTX. CONCLUSION: BAERs are useful to distinguish CMTX from CMT1A and may assist selection of appropriate patients for connexin32 mutation analysis.

Adolescent↗
PubMed1994

Cognitive dysfunction following subcortical infarction.

OBJECTIVE: To determine the association between computed tomographic scan findings of subcortical infarction, periventricular lucency, and ventricular enlargement and a patient's performance on a range of neuropsychological tests. DESIGN: Prospective study of patients in whom computed tomographic scanning identified discrete areas of subcortical lucency that were consistent with multiple subcortical infarcts and in whom there was no evidence for additional cerebral computer tomographic pathology. SETTING: Hospital practice that included both inpatients and ambulatory patients. PATIENTS: One hundred forty-seven consecutive appropriate computed tomographic scans were identified. Sixty-two patients were excluded because of concomitant medical disorders, and eight refused participation. We describe 77 patients. MAIN OUTCOME MEASURES: Performance on a battery of neuropsychological tests. RESULTS: The number of infarcts but not the volume of infarction, periventricular lucency, and cerebral ventricular enlargement but not cortical atrophy were significantly associated with impaired performance on neuropsychological tests. The number of infarcts correlated with impaired performance on tests, and this impaired performance was thought to be dependent on the function of frontal systems, while periventricular lucency and ventricular enlargement correlated with impaired performance on a wider range of tests, including tests that depended on memory and language. CONCLUSIONS: The number of infarcts, periventricular lucency, and ventricular enlargement are the computed tomographic head scan parameters that correlated with severity of impaired performance on neuropsychological tests in patients with subcortical infarction. Cognitive impairment is presumed to be the result of cortical disconnection following disruption of the connections between the subcortical regions and the frontal cortex.

Aged↗
PubMed1994

A yeast RNA-binding protein shuttles between the nucleus and the cytoplasm.

RNA-binding proteins have been suggested to move in association with RNA as it leaves the nucleus. The NPL3 gene of the yeast Saccharomyces cerevisiae encodes in nuclear protein with consensus RNA-binding motifs and similarity to heterogeneous nuclear ribonucleoproteins and members of the S/R protein family. We show that although Npl3 is located in the nucleus, it can shuttle between nuclei in yeast heterokaryons. In contrast, other nucleus-targeted proteins do not leave the nucleus under similar conditions. Mutants missing the RNA-binding motifs or the N terminus are still capable of shuttling in and out of the nucleus. Npl3 mutants missing the C terminus fail to localize to the nucleus. Overproduction of Npl3 in wild-type cells shows cell growth. This toxicity depends on the presence of series of unique repeats in the N terminus and localization to the nucleus. We suggest that the properties of Npl3 are consistent with it being involved in export of RNAs from the nucleus.

Biological Transport↗
PubMed1993

Sex differences and the role of aromatization in the control of sexually dimorphic behavior and morphology in gray short-tailed opossums (Monodelphis domestica).

Sex differences in the activating effects of an aromatizable (testosterone, T) and a nonaromatizable (dihydrotestosterone, DHT) androgen on sexually dimorphic scent marking and aggressive behavior were examined in gonadectomized gray short-tailed opossums. When compared with males, females showed less chest, head, flank, and hip marking and more fighting behavior in tests with stimulus females and threat behavior in tests with stimulus males following receipt of subcutaneous T, DHT, or blank (B) implants. Testosterone but not DHT activated hip and head marking while both T and DHT activated flank marking. In tests with stimulus females, only males showed clicking vocalizations and T but not DHT or B stimulated clicking. Animals that received T had significantly larger suprasternal scent glands than those that received DHT or B. The significance of these findings is discussed with respect to the development of sex differences in behavior in eutherian mammals.

Aggression↗
PubMed1992

Banking on breast milk.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The transient expression of type II collagen at tissue interfaces during mammalian craniofacial development.

Using immunocytochemical techniques, the spatiotemporal distribution of the major collagen isoform of cartilage, type II collagen, has been investigated during early craniofacial development in the mouse embryo. Early and transient expression was associated with the otic and optic vesicles, the ventrolateral surfaces of the developing brain, olfactory conchi, endocardial and mesocardial tissues, the lateral and basal surfaces of the pharyngeal endoderm and beneath the ectoderm of the branchial arches. A number of these locations are sites of epithelial-mesenchymal tissue interaction believed to generate the component parts of the chondrocranium; here, type II collagen appears transiently in advance of overt chondrogenesis in the mesenchyme. At such sites, immunofluorescence is typically localised along the basal surface of the epithelial partner, with the strongest reaction detected between the basal aspects of the otic and rhombencephalic epithelia. Immunoelectron microscopy, using pre-embedding immunostaining and a protein G-gold technique, reveals that the type II collagen is adjacent to, but not integral with, the basal laminae. Gold particles are clearly associated with 10-15 nm fibrils of the extracellular matrix in the reticulate lamina region. The pattern of type II collagen expression in the mouse closely correlates with that demonstrated previously in the quail, indicating a high degree of phylogenetic conservation between these two vertebrate species. These findings are consistent with the hypothesis that the pattern of epithelial secretion of type II collagen, or a coexpressed matrix molecule, constitutes a morphogenetic signal, realised as a matrix-mediated tissue interaction, and specifying the form of the vertebrate chondrocranium. Three-dimensional reconstruction of early type II collagen distribution, and of the subsequent chondrocranial cartilages, reveals that chondrocranial form can be derived from a 'pre-pattern' of epithelially derived type II collagen expressed at epithelial-mesenchymal tissue interfaces.

Animals↗
PubMed1989

Candidiasis-endocrinopathy syndrome with progressive myopathy.

A women suffering from the candidiasis-endocrinopathy syndrome, developed severe myopathy in her fourth decade and died from it at the age of 37 years. Associated conditions were hypoparathyroidism, vitiligo, chronic mucocutaneous candidiasis, short stature, intellectual disability, ovarian failure and alopecia totalis. Muscle biopsy findings were non-specific with focal atrophy of type 2 fibres. Serum immunoglobulin levels were normal. The only demonstrable abnormalities of her immune system were impaired T-cell function and antibody production by B-cells (detectable to smooth muscle, mitochondria and gastric parietal cells). The T-cell abnormality may have been part of a more generalized cell defect, resulting from an unidentified genetic abnormality, whilst the circulating antibodies could have been a response to tissue damage. There was no convincing evidence of primary autoimmune damage.

Adult↗
PubMed1984

Effect of acetazolamide on insulin sensitivity in myotonic disorders.

Acetazolamide is effective treatment for myotonia in certain patients with myotonia congenita. Since potassium metabolism may be abnormal in myotonia congenita, we studied the effect of acetazolamide administration on potassium regulation and glucose disposal, using the euglycemic insulin clamp technique in patients with myotonic disorders and in normal subjects. Glucose disposal was normal in patients with myotonia congenita; administration of acetazolamide increased glucose disposal in normal subjects and in patients with myotonia congenita. By contrast, patients with myotonic dystrophy showed insulin resistance and decreased glucose disposal that was not improved by acetazolamide administration. Patients with myotonia congenita had elevated potassium levels in the basal state and a greater fall in potassium level during the insulin clamp procedure than controls. Patients with myotonic dystrophy had normal or low basal potassium levels and a subnormal decrease in potassium level during the insulin clamp procedure. Administration of acetazolamide did not alter these abnormalities in potassium metabolism in patients with either myotonia congenita or myotonic dystrophy.

Acetazolamide↗