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Biomedical subjects

M Hall

Publications and source records attributed to M Hall.

At least 19 recordsLinked to original sources
PubMed1992

Characterisation and correction of a mammalian cell mutant defective in late step of base excision repair.

An Indian muntjac cell line, SVM, is unusually sensitive to cell killing induced by a range of alkylating agents. Cells transfected with the Escherichia coli ada gene or human genomic DNA have allowed the response of SVM to alkylating agents to be dissociated into two distinct components. Thus, in SVM, which expresses very low levels of alkyltransferase (AT), O6-alkylguanine appears to be the major cytotoxic, clastogenic, and recombinogenic lesion following exposure to agents such as methylnitrosourea (MNU). However, SVM is also very sensitive to agents such as dimethylsulfate (DMS), which produce only very low levels of O6-methylguanine damage. Sensitivity to DMS resides in an inability to complete base excision repair, with the appearance of persistent single-strand DNA breaks (SSBs), and does not appear to involve defects in glycosylase, apurinic/apyrimidinic endonuclease, or DNA ligase activities. Another, possibly related, phenotypic trait in SVM is its limited ability to ligate transfected linear plasmid DNA. Transfectants of SVM, harboring human DNA sequences, show a significant correction of DMS-induced cytotoxicity and clastogenicity and a reduction in the levels of DMS-induced DNA SSBs. The DMS-resistant transfectants have an increased ability to ligate linear plasmid DNA, and also express AT, making these lines resistant to alkylating agents such as MNU. These results suggest that cells possess a mechanism that regulates AT expression, plasmid break-joining ability, and certain aspects of base excision repair. Transfectants of SVM containing human DNA provide a means to isolate genes involved in a coordinate response to alkylation damage.

Alkylating Agents↗
PubMed1992

A hypothesis for the higher incidence of vesico-ureteral reflux and primary megaureters in male babies.

The authors propose a new explanation for the male preponderance in cases with prenatally diagnosed vesico-ureteral reflux and primary megaureters. The theory is based on conclusions drawn from the characteristics of 4 patients (3 perinatal cases and 1 occurring in a 14-year-old boy) presenting with unusual anomalies of the lower urinary tract. In this hypothesis, the male preponderance could be related to an abnormal dilatation of the posterior urethra occurring during the embryological development of the male urethra. The dilatation leads to a flap valve mechanism and to a functional obstruction of the bladder outlet and finally to secondary dilatation of the upper urinary tract. This obstruction may be transitory; reflux and megaureters found in utero or after birth could be considered as sequellae of this phenomenon.

Adolescent↗
PubMed1992

Osteomesopyknosis: a benign familial disorder of bone.

A family with osteomesopyknosis is described. This condition is a rare benign bone dysplasia, characterized by patchy sclerosis predominantly involving the axial skeleton. The radiographic appearances may be confused with osteoblastic metastases, renal bone disease and other sclerosing bone disorders. As routine blood tests and isotope bone scans are normal in osteomesopyknosis, differentiation is readily achieved.

Aged↗
PubMed1992

Cost-effectiveness of present programs for detection of asymptomatic hypertension in relation to the severity of hypertension and proteinuric hypertension.

Proteinuric hypertension is an important cause of maternal and perinatal mortality. Eclampsia cannot always be prevented. The likelihood of identifying a new case of proteinuric hypertension at any particular visit is very low using traditional antenatal care schedules, and care could be focused on women at higher risk.

Cost-Benefit Analysis↗
PubMed1992

Polyclonal immunoglobulin therapy protects against cardiac damage in experimental coxsackievirus-induced myocarditis.

Balb/c male mice infected i.p. with 2 x 10(5) plaque forming units (PFU) of coxsackievirus B3 (CVB3) develop severe myocarditis 7 days later. Studies were performed to determine whether therapy with normal polyclonal immunoglobulin would prevent cardiac inflammation. Partially purified immunoglobulin was derived from pooled mouse serum by ammonium sulphate precipitation. Infected animals given either 100 or 1000 micrograms of this preparation for 2 days prior to infection showed greater than 50% reduction in myocarditis compared to control animals which were infected and given either phosphate buffered saline, human immunoglobulin or monoclonal mouse IgG to an extraneous antigen. Protection did not depend upon inhibition of virus infection since cardiac viral titres were frequently equivalent in control and immunoglobulin-treated groups.

Animals↗
PubMed1992

Multidisciplinary approaches to management of acute head injury.

The formation of a multidisciplinary head injury team at St. Michael's Hospital has served to improve the quality of care for acutely head-injured patients. The multidisciplinary team follows the patient from the neurosurgical intensive care unit to the early rehabilitation phase. Treatment for the patient and family focuses on physical, cognitive and psychosocial areas. Cooperation of the various medical and paramedical professionals facilitates earlier and more comprehensive treatment for patients and their families, while enhancing research.

Communication↗
PubMed1992

Comparison of fetal rabbit brain xenografts to three different strains of athymic nude rats: electrophysiological and immunohistochemical studies of intraocular grafts.

Interest in the use of neural tissue transplantation for the study of CNS development and maturation and the potential use of this technique for the treatment of certain degenerative CNS disorders has led to our use of transplantation of neural tissue across species lines. Prior to extensive transplantation studies using athymic rats as recipients, we wished to evaluate the currently available strains of athymic rat for their suitability as host animals for xenografts of neural tissue. Fetal cerebellar and cerebral cortex tissue from rabbit brain of gestational age 20-25 days was dissected and transplanted to the anterior chamber of the eye of Harlan Wisconsin, Fisher 344 Jnu, or NCI-Harlan athymic nude rat strains. The brain tissue grafts were allowed to mature for 3 mo during which time the size and vascularity of each graft was monitored through the cornea of anesthetized hosts. In each group all of the transplants survived and grew to varying extents in the anterior chamber of the eye. Following the growth study in vivo extracellular recording of single neuronal activity was performed. Spontaneous neural activity was found in most transplants in all three groups with no difference in the viability or discharge rates of neurons between the groups. Illumination of the ipsilateral eye increased the firing rate of neurons in all three groups, suggesting excitatory cholinergic innervation of the grafted neurons from the host parasympathetic iris ground plexus. Antibodies directed against neurofilament protein, glial fibrillary acidic protein, synapsin, and tyrosine hydroxylase were used to characterize the transplants immunocytochemically and revealed no differences between the grafts in the three groups of recipients. All transplants contained significant numbers of glial and neuronal elements with the distribution resembling that in adult brain tissue. Some of the transplants contained a sparse innervation of tyrosine hydroxylase-positive fibers from the sympathetic plexus of the host iris. Furthermore, synapsin-immunoreactivity suggested that synaptogenesis had taken place within the grafts. Histological examination of the grafts revealed that 67% of the grafts had been infiltrated, to varying extents, by lymphocytes which led to areas of cell lysis and necrosis. All host animals had populations of T-cell receptor positive cells, most of which also expressed the T-cell surface antigens CD4 and CD8. However, no transplants were overtly rejected over the 15 wk period of study.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Visual destabilisation of posture in normal subjects.

A new and simple method of assessing reliance on vision for postural control was evaluated in 41 normal subjects. Left-right reversal of peripheral vision induced by a head-mounted mirror device caused an initial dramatic instability in approximately half the subjects, when standing on foam to reduce the value of proprioception. Lateral reversal of central vision by means of a prism device evoked similar responses. Sensitivity to vision reversal was significantly correlated with motion sickness susceptibility. Despite some rapid habituation (partially retained over several weeks) sway remained as great as with eye closure in the anterior-posterior as well as lateral direction, indicating complete suppression of the visual input. Balancing with vision reversal caused a selective decrement in performance of a visuo-spatial memory task, suggesting that coping with misleading visual input may place continuous demands on cortical spatial processing.

Adult↗
PubMed1991

Identification of pathological mineral deposits by Raman microscopy.

Raman microscopy--the analysis of scattered photons after excitation--is well established in non-biological sciences for the identification of crystals. It shows promise in biological (clinical) specimens also, as demonstrated here in studies of synovial fluid, synovium, and gouty tophus, selected for their known content of sodium urate and calcium pyrophosphate crystals.

Aged↗
PubMed1991

The ocular effects of gases when injected into the anterior chamber of rabbit eyes.

We studied the toxic effects of sulfur hexafluoride and perfluoropropane in comparison with air, balanced salt solution, hyaluronate sodium, and aqueous humor in a rabbit model. Sixty normal pigmented rabbits were studied during a period of 4 weeks. The variables studied were slit-lamp biomicroscopic examination of the anterior segment, intraocular pressure as measured by pneumotonometry, corneal thickness and endothelial cell count as measured by specular microscopy, lens opacity by Scheimpflug photography, and light and transmission electron microscopy. All three gases were more toxic to the cornea and lens than were balanced salt solution, hyaluronate, and aqueous humor. However, 15% perfluoropropane and 50% sulfur hexafluoride were no more toxic to the eye than air was. Therefore, this study suggests that nonexpansile mixtures of perfluoropropane and sulfur hexafluoride may be beneficial and relatively safe in re-forming persistently flat anterior chambers in situations where the use of air is being considered.

Air↗
PubMed1991

Renal duplications: the impact of perinatal ultrasound on diagnosis and management.

Perinatal urology is a rapidly expanding field in pediatric urology bringing significant changes in the diagnosis and management of congenital uropathies. Renal duplication was detected by antenatal and perinatal ultrasound in 19 cases (22 duplicated systems). In most cases, no precise diagnosis could be established in utero (4 of 13), but this lack of accuracy is of little clinical significance since all newborns with suspected uropathies undergo complete urological investigations in the perinatal period. Voiding cystogram demonstrated reflux in 11 of 22 cases. On postnatal urography a functioning upper pole was demonstrated in 11 of 22 kidneys. There were 12 ureteroceles: in 8 a nonfunctioning upper pole was removed, while 3 were endoscopically incised with good functional improvement and 1 was reimplanted. Early recognition of congenital uropathies in association with duplication by prenatal ultrasound significantly improves patient care allowing early postnatal relief of obstruction by less invasive methods and before infection or persistent obstruction worsens the prognosis.

Congenital Abnormalities↗
PubMed1991

Papilloedema and cranial nerve palsies complicating apparent benign aseptic meningitis.

Three patients who presented with apparently uncomplicated aseptic meningitis subsequently developed papilloedema and sixth cranial nerve palsies between 11 and 16 days after the onset of the illness. All three patients recovered completely without treatment. Raised intracranial pressure is a poorly recognized complication of aseptic meningitis that may represent a post-infective or 'allergic' response to an enteroviral infection. While clinicians should be aware of this possible complication of aseptic meningitis, differentiation from tuberculous meningitis may be difficult necessitating empirical treatment with anti-TB drugs.

Abducens Nerve↗
PubMed1991

A new case of acro-renal-ocular (radio-renal-ocular) syndrome with cleft palate and costo-vertebral defects? A brief clinical report.

The authors describe a girl with retarded growth, renal malformations, retinal coloboma and hypoplasia of the thumbs like reported in the acro-renal-ocular syndrome. In addition, they found defects of the ribs and spine and cleft palate, not previously described in this syndrome. The was noted to have minor anomalies of the hands, which might represent a mild manifestation of this autosomal dominant syndrome.

Abnormalities, Multiple↗