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Biomedical subjects

W Wu

Publications and source records attributed to W Wu.

At least 433 records · Page 24Linked to original sources
PubMed1993

Phosphohistidine and phospholysine phosphatase activities in the rat: potential protein-lysine and protein-histidine phosphatases?

We have detected phosphohistidine and phospholysine phosphatase activities in rat tissue extracts using partially phosphorylated, high-molecular-mass (> 10 kDa) polymers of histidine and lysine as substrates. Multiple phosphohistidine- and phospholysine-specific phosphatases were present in these extracts based on observed differences in heat stability, sensitivity to bivalent metal ions and thiol modifying reagents, and/or elution from DE-52 cellulose. The properties of these phosphohistidine and phospholysine phosphatases were distinct from those of the phosphomonoester-specific protein phosphatases or the N-P phosphohydrolases that act on the free phosphoamino acids phosphoarginine, 3-phosphohistidine or phospholysine.

Animals↗
PubMed1993

Inhibition of nitric oxide synthase reduces motoneuron death due to spinal root avulsion.

Our previous studies have shown that nitric oxide synthase (NOS) can be induced in motoneurons after spinal root avulsion lesion and the lesion-induced NOS is coincident with the death of the injured neurons. The present study examined whether the death of injured motoneurons can be prevented by inhibition of NOS. Nitroarginine, a specific inhibitor of NOS, was injected into adult rats which underwent spinal root avulsion. At a dose of 50 mg/kg/day, nitroarginine significantly inhibited the activity of lesion-induced NOS and significantly reduced the death of motoneurons due to spinal root avulsion. Results of the present study indicate that NO, produced by lesion-induced NOS, may be involved in and responsible for the neuronal death after traumatic injury.

Amino Acid Oxidoreductases↗
PubMed1993

Evidence that the loss of homeostatic signals induces regeneration-associated alterations in neuronal gene expression.

Axotomy of motoneurons leads to upregulation of T alpha 1 alpha-tubulin and p75 NGF receptor mRNAs. To distinguish whether these increases are due to interruption of ongoing homeostatic signals or to positive factors derived from non-neuronal cells of the injured nerve, we developed an experimental paradigm that allowed us to selectively block some facets of axonal signaling without initiating a peripheral nerve injury response. More specifically, the marginal mandibular and buccal branches of the facial nerve were locally cooled to 4-8 degrees C (a cold block) for 36-60 hr. This treatment effectively and reversibly blocked fast axonal transport, as monitored by the ability of facial motor neurons to retrogradely transport fluorogold from their terminals to their cell bodies. Light microscopy of semithin epoxy sections demonstrated that the cold block treatment did not lead to macrophage invasion or to morphological alterations in the nerve either proximal or distal to the cold block region. In situ hybridization and image analysis of retrogradely labeled facial motor neurons indicated that such a cold block induced T alpha 1 alpha-tubulin and p75 NGF receptor mRNAs to the same level as did a corresponding nerve transection. In contrast, T26 alpha-tubulin mRNA, which does not increase following axotomy, was not affected by the cold block treatment. These results suggest that neurons sense their status by a constant flow of information carried, circulated, or maintained by fast axonal transport and that the axotomy-induced increases in T alpha 1 and p75 NGF receptor mRNAs in motor neurons are, to a great extent, due to loss of such homeostatic signals.

Animals↗
PubMed1993

Expression of nitric-oxide synthase (NOS) in injured CNS neurons as shown by NADPH diaphorase histochemistry.

Recent studies have implicated nitric oxide (NO) in several mechanisms related to neuronal degeneration and synaptic plasticity. In the present study, two models of traumatic neuronal injury were used to examine the expression of NOS following neuronal injury and its relationship to axonal sprouting and neuronal degeneration. It was found that NOS is induced in a week of axonal injury in neurons that are normally NOS-negative. Spinal motoneurons express the enzyme after ventral root avulsion, but not after ventral root transection. Neurons of the nucleus dorsalis of the spinal cord express NOS after ipsilateral spinal cord hemisection. These two models provide information about the time course of NOS expression in injured neurons and the opportunity in future studies to determine the role of NOS and its product, NO, in CNS injury. Observations from the present study suggest that early NOS expression seems to be associated with axonal sprouting and growth. Interestingly, though, the neurons expressing lesion-induced NOS ultimately die. Whether NOS expression in these cells is related to their death is currently under investigation.

Amino Acid Oxidoreductases↗
PubMed1993

Development of nitric oxide synthase expression in the superficial dorsal horn of the rat spinal cord.

Development of nitric oxide synthase (NOS) expression in the superficial dorsal horn of the rat spinal cord was studied using NADPH diaphorase histochemistry. At birth, no positive staining was seen in the superficial laminae of the cord. A week later, a few small positive neurons and fibers were seen in presumptive lamina II. The adult pattern of NOS expression was evident by the end of the third postnatal week.

Amino Acid Oxidoreductases↗
PubMed1993

Increased expression of nitric oxide synthase in hypothalamic neuronal regeneration.

This investigation deals with the histochemical and scanning electron microscopic (SEM) correlates that depict regeneration of the neurohypophyseal system that may be nitric oxide dependent following hypophysectomy in the rodent hypothalamus. NOS histochemistry and correlative SEM were employed to establish the rates of regrowth and appearance of NOS-positive supraoptic (SON) and paraventricular (PVN) neurites and their cell bodies following hypophysectomy. NOS activity increased significantly in SON and PVN neuronal perikarya and regenerating axons by 2 weeks. NOS-positive neurites were observed to regrow into the adjacent median eminence and insinuate into the lumen of the third cerebral ventricle. By 4 weeks posthypophysectomy, NOS staining of SON and PVN neurons and their regrown neurites had returned to normal control levels. Despite this fact, large complexes of apparent magnocellular neurites remained upon the floor of the third cerebral ventricle as observed with SEM. These observations support the hypothesis that NO may play a fundamental role in the process of regeneration, plasticity, and retargeting of SON and PVN axons following injury.

Amino Acid Oxidoreductases↗
PubMed1993

Transplantation of the mammalian pineal gland: studies of survival, revascularization, reinnervation, and recovery of function.

The survival, revascularization, reinnervation, and recovery of function of transplanted rat pineal glands were studied following grafting into four different locations in pinealectomized rats. Pineal grafts were well vascularized by fenestrated capillaries. Pinealocytes in the grafts maintained high-metabolic activity. More nerve fibers and terminals were observed in the grafts within the anterior chamber of the eye than in the third cerebral ventricle and the pineal region (in situ transplantation). No fibers or terminals were found in grafts placed beneath the renal capsule. Nighttime serum melatonin levels increased significantly in pinealectomized rats with transplants into either the third cerebral ventricle or the anterior eye chamber. This increase might reflect graft reinnervation. Yet day-night differences in serum melatonin were observed only in host rats receiving transplants in the anterior eye chamber. In conclusion, pinealocytes survived transplantation into different locations and exhibited ultrastructural features indicative of active secretory processes; however, day-night differences in serum melatonin are only restored following transplants into the anterior eye chamber. Reinnervation of the grafts by the host superior cervical ganglion is necessary for this restoration.

Animals↗
PubMed1993

Localization of metallothionein in breast carcinomas. An immunohistochemical study.

Metallothionein (MT) is a cysteine-rich, low molecular weight protein that binds zinc, copper, and cadmium. It is present in a number of normal cells including hepatocytes particularly during fetal and early postnatal life. It has been suggested that developmental profile of MT is similar to other oncofetal gene products and hence, it could be used as a marker for aggressive tumour behaviour. In order to test that hypothesis, we used a monoclonal antibody to MT and immunohistochemically evaluated formalin-fixed, paraffin-embedded tissues from 79 breast carcinomas. In non-neoplastic breast tissue, a strong nuclear and cytoplasmic staining was observed in myoepithelial cells. Positive staining for MT was present in 35 (44%) of breast carcinomas. In most positive cases, nuclear, or both nuclear and cytoplasmic staining was seen. All positive tumours were invasive ductal carcinomas, including a medullary and a metaplastic carcinoma. None of the mucinous, lobular, or intraductal papillary carcinomas reacted for MT. A statistically significant association was found between MT immunostaining and histological grade (P < 0.01) as well as with nuclear grade (P < 0.01). We also observed an inverse relationship between MT staining and oestrogen receptor content of tumours (P < 0.01). Similarly, a statistically significant association was found between moderate and strong MT immunostaining and decreased overall survival and shorter disease-free survival (P < 0.01). MT immunostaining was also predictive of a worse prognosis in the subgroup of lymph node negative (P < 0.001) and oestrogen receptor negative patients (P < 0.01). No statistically significant association was found between MT staining and size of tumour or the presence of lymph node metastasis. We conclude that MT staining may be a useful marker of less differentiated and more aggressive carcinomas of the breast.

Breast Neoplasms↗
PubMed1993

Nicotine-induced analgesia in rats: the role of calcium and the diversity of responders and nonresponders.

Following a single dose of nicotine, (NIC, 1 mg/kg s.c.), 60% of tested rats revealed significant antinociception as measured by the tail-flick (TF) test, and were classified as responders, with those in which TF latencies did not change, nonresponders. The following experiments were carried out one week later. In nonresponders, pretreatment with ethylenediaminetetraacetic acid (EDTA, 250 microM/kg s.c. four times every 15 min) followed by 1 mg NIC, produced significant analgesia in 50% of rats, to the same magnitude as did nicotine alone (1 mg) in responders. The other 50% of rats which failed to respond to EDTA pretreatment, all revealed similar analgesia following the higher dose of NIC (1.5 mg/kg s.c.), with similar side effects, as generally observed in responders. In responders, pretreatment with CaCl2 (1.5 mM/kg s.c.) completely abolished NIC (1 mg/kg s.c.)--induced analgesia in all rats. Our data provide stronger evidence and a further verification that EDTA potentiates, whereas CaCl2 completely abolishes, nicotine-induced analgesia in rats; supporting our hypothesis of the involvement of calcium ions in this effect.

Analgesia↗
PubMed1993

Organization of the serotonergic innervation of spinal neurons in rats--III. Differential serotonergic innervation of somatic and parasympathetic preganglionic motoneurons as determined by patterns of co-existing peptides.

The spinal cord is innervated by brainstem serotonergic neurons, some of which contain substance P and/or thyrotropin-releasing hormone in addition to serotonin. These neurons project at least three types of axons to the spinal cord: those containing both substance P and thyrotropin-releasing hormone, those containing thyrotropin-releasing hormone but not substance P, and those containing neither substance P nor thyrotropin-releasing hormone. However, the organization of the different types of serotonergic processes is unclear. In the present studies, the types of serotonergic axons projecting to two kinds of spinal neurons were examined. Somatic and parasympathetic preganglionic motoneurons were labeled retrogradely from the pelvic or sciatic nerve, respectively. Sections containing these neurons were stained either for serotonin and substance P, or for serotonin and thyrotropin-releasing hormone. Of a total of 428 profiles examined that were retrogradely labeled from the sciatic nerve, 425 (99%) were apposed by serotonin-immunoreactive varicosities; similarly, of a total of 382 profiles examined that were retrogradely labeled from pelvic nerve, 353 (92%) were apposed by serotonin-immunoreactive varicosities. However, differences appeared to exist between the types of serotonergic varicosities innervating these two groups of neurons. Among the profiles labeled from the sciatic nerve, it was estimated that over 97% were apposed by serotonin-immunoreactive varicosities in which serotonin co-existed with substance P and thyrotropin-releasing hormone. In contrast, among the profiles labeled from pelvic nerve that were apposed by serotonin-immunoreactive varicosities, it was estimated that less than 1% were apposed by serotonin-immunoreactive varicosities containing both thyrotropin-releasing hormone and substance P. We estimate that most of the remainder (about 80%) were apposed by serotonin-immunoreactive varicosities containing thyrotropin-releasing hormone but not substance P. We conclude that both the cell bodies of neurons retrogradely labeled from the pelvic nerve and those labeled from the sciatic nerve were apposed by serotonin varicosities. However, these two systems of neurons appear to be innervated largely by two different populations of serotonergic cells. This suggests that the raphe-spinal serotonergic system may independently modulate the activities of somatic motoneurons and parasympathetic preganglionic motoneurons.

Animals↗
PubMed1993

Developmentally-regulated cell surface N-linked oligosaccharides participate in intercellular cohesion in Dictyostelium discoideum.

The ability of purified plasma membrane glycoconjugates to inhibit the EDTA-resistant agglutination between aggregation-stage cells of Dictyostelium discoideum has suggested that receptor binding of these glycoconjugates provides a basis for cell-cell cohesion during aggregation. This has been tested by analysis of a series of mutants with different defects in the assembly of N-linked oligosaccharides. Mutant HL241 lacks outer branch components of N-linked oligosaccharides and fails to aggregate or express EDTA-resistant cohesion. HL244 makes unsulphated but otherwise normal N-linked oligosaccharides, generates multiple tips on aggregated cell mounds in some clones, and shows abnormally strong EDTA-resistant cohesion. Two mutants that are temperature-sensitive for complete processing of N-linked oligosaccharides are also temperature-sensitive for expression of both aggregation ability and EDTA-resistant cohesion. A revertant that recovered essentially normal N-linked oligosaccharide processing at the restrictive temperature has also recovered its ability to aggregate and to agglutinate in EDTA.

Agglutination↗
PubMed1993

Evidence for amelioration of cellular damage in ischemic rat brain by radix salviae miltiorrhizae treatment--immunocytochemistry and histopathology studies.

The changes of somatostatin (SS)--like immunoreactive cells and morphology were observed in the models of ligation of right MCA and bilateral ligation of CCA respectively. The results showed: (1) a decline of SS immunoreactive nerve cell profiles in right cerebral cortex after 3h ligation of MCA as compared with left cerebral cortex and sham-operated group, while no significant difference was found between RSM-treated and saline-treated groups; (2) selective ischemic cell changes in cerebral cortex, hippocampus and caudate nucleus after 3h ligation of CCA. The changes included shrinkage and condensation of perikaryon, nuclear pyknosis, cytoplasmic eosinophilia in some neurons. The ischemic changes were more severe in saline-treated group than RSM-treated group. The experiments indicated that the selective ischemic cell changes could be improved by RSM, suggesting that treatment to modulate SS metabolism may be indicated after ischemic insults.

Animals↗
PubMed1993

[PCR amplification of the leptospiral DNAs from different genus and species with the variable sequences of 16S rRNA gene].

We designed a pair of primers from the variable regions (V2 and V4) of 16S rRNA gene of Leptospira interrogans, i. e. PI: 5'GGG AAC CTA ATA CTG GAT GG; PII: 5' ACA TAG TTT CAA GTG GAG GC, and amplified the leptospiral DNAs from different genus and species. When denaturing with 55 degrees C, all DNAs of L. interrogans had the same products not only in length but also with Kpn I-digested pattern. The DNA of L. biflexa could be amplified with a c. a. 280 bp-band but not digested by Kpn I, while the DNAs of Leptonema and other control bacteria had no amplification. In addition, the products of L. interrogans spp. could be hybridized with the PCR product of L. interrogans serovar lai strain Lai labelled with 32P, while the product of L. biflexa had no hybridization. It proved that the 16S rRNA gene primers is useful for the classification and detection of leptospires.

Base Sequence↗