Search PubMed⌕ Search

Biomedical subjects

H H Ho

Publications and source records attributed to H H Ho.

At least 55 records · Page 3Linked to original sources
PubMed1993

Reversible motor neuron disease.

We investigated a 69-year-old male with a clinical syndrome resembling amyotrophic lateral sclerosis characterized by fasciculation, wasting of the limb muscles and increased deep tendon reflexes in the lower limbs. Electromyographic (EMG) studies showed abundant positive sharp waves and fibrillation potentials with decreased recruitment in the limbs and paraspinal muscles. The patient recovered almost completely in approximately 1.5 years, and follow-up EMG studies showed no positive sharp waves or fibrillation potentials in the limb muscles except for some polyphasic motor units in the bilateral intrinsic hand muscles. No known systemic disease, malignancy or heavy metal intoxication was found during the course of his illness. So far, there are only few cases reported with spontaneous remission of motor neuron disease; however, the possibility should always be considered.

Aged↗
PubMed1992

Systemic lupus erythematosus and pheochromocytoma.

A 40-year-old Chinese woman with systemic lupus erythematosus (SLE) developed labile blood pressure 3 years after her onset of high blood pressure. Pheochromocytoma was subsequently found and removed. Postoperatively her hypertension improved without change in her SLE activity. Our case demonstrates pheochromocytoma can be a cause of hypertension in SLE.

Adrenal Gland Neoplasms↗
PubMed1989

Antimitotic natural products combretastatin A-4 and combretastatin A-2: studies on the mechanism of their inhibition of the binding of colchicine to tubulin.

Combretastatin A-4 (CS-A4), 3,4,5-trimethoxy-3'-hydroxy-4'-methoxy-(Z)-stilbene, and combretastatin A-2 (CS-A2), 3,4-(methylenedioxy)-5-methoxy-3'-hydroxy-4'-methoxy-(Z)-stilbene, are structurally simple natural products isolated from the South African tree Combretum caffrum. They inhibit mitosis and microtubule assembly and are competitive inhibitors of the binding of colchicine to tubulin [Lin et al. (1988) Mol. Pharmacol. 34, 200-208]. In contrast to colchicine, drug effects on tubulin were not enhanced by preincubating CS-A4 or CS-A2 with the protein. The mechanism of their binding to tubulin was examined indirectly by evaluating their effects on the binding of radiolabeled colchicine to the protein. These studies demonstrated rapid binding of both compounds to tubulin even at 0 degrees C (binding was complete at the earliest times examined), in contrast to the relatively slow and temperature-dependent binding of colchicine. Although the binding of the C. caffrum compounds to tubulin was quite tight, permitting ready isolation of near-stoichiometric amounts of drug-tubulin complex even in the absence of free drug, both CS-A4 and CS-A2 dissociated rapidly from tubulin in the presence of high concentrations of radiolabeled colchicine. Apparent rate constants for drug dissociation from tubulin at 37 degrees C were 3.2 x 10(-3) s-1 for CS-A4, 4.8 x 10(-3) s-1 for CS-A2, and 2.9 x 10(-5) s-1 for colchicine (half-lives of 3.6, 2.4, and 405 min, respectively). Thus, the effectiveness of the C. caffrum compounds as antimitotic agents appears to derive primarily from the rapidity of their binding to tubulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Tubulin-dependent hydrolysis of guanosine triphosphate as a screening test to identify new antitubulin compounds with potential as antimitotic agents: application to carbamates of aromatic amines.

Tubulin-dependent GTP hydrolysis was evaluated for its potential as a relatively simple screening assay for new antimitotic drugs. Carbamates of aromatic amines were chosen as the test system because of the relatively diverse structures of compounds in this class already known to have antimitotic properties and because of the large number of such compounds in the NSC collection of the National Cancer Institute. Of 162 compounds evaluated, significant alterations in the GTPase reaction were observed with 26 agents. Sixteen of these had substantial inhibitory effects on tubulin polymerization (true positives), while ten did not (false positives). There were no false negatives (i.e., no agent inactive in the GTPase assay inhibited tubulin polymerization). The true positives were examined for effects on cell growth and mitosis, and four compounds had 50% inhibitory concentration values of 2 microM or less with L1210 murine leukemia cells. All four caused the accumulation of cells in metaphase arrest. We conclude that tubulin-dependent GTP hydrolysis can be used effectively to select new antitubulin compounds with potential as antimitotic agents from a large group of compounds of unknown activity.

Antineoplastic Agents↗
PubMed1989

Reiter's syndrome in uremia: report of a case.

A 35-year-old male uremic patient developed the classical presentation of Reiter's syndrome after 3 years of regular hemodialysis. He had painful swelling of the left knee, sacroilitis, urethritis, balanitis, painless oral ulcers, acute uveitis and positive HLA-B27. Disease activity persisted and was aggravated although immune function studies showed depressed cellular immunity. The clinical course of this patient seemed to contradict our belief that activity of immunologically mediated disease will abate after uremia, but it concurred with the report that Reiter's activity was unchanged in AIDS despite the significant immunodeficiency of AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Association of ankylosing spondylitis with IgA-multiple myeloma: report of a case and pathogenetic considerations.

Multiple myeloma has rarely been reported in patients with ankylosing spondylitis. We observed a patient with a 20-year history of ankylosing spondylitis, who subsequently developed IgA myeloma. This association may not be simply coincidental. It has been proposed that the protracted stimulation of immunocytes by inflammatory lesions on the mucosal surfaces of the gastrointestinal, respiratory, and biliary tracts, where lymphocytes are already committed to IgA production, may be implicated in the pathogenesis of IgA myeloma in some patients. Ankylosing spondylitis is a chronic inflammatory disease, probably resulting from the interaction of a genetic predisposition involving HLA-B27 with an environmental event such as enteric bacterial infection. We propose that ankylosing spondylitis and IgA myeloma occurring concomitantly in our patient implies a possible pathogenetic relationship. In ankylosing spondylitis, persistent reticuloendothelial stimulation, due to chronic subclinical gastrointestinal infection, may lead to IgA-producing plasma cell activation and proliferation, and subsequent IgA myeloma development.

Humans↗
PubMed1988

Cornigerine, a potent antimitotic Colchicum alkaloid of unusual structure. Interactions with tubulin.

Cornigerine is a natural product analog of colchicine produced by Colchicum cornigerum in which the vicinal 2- and 3-methoxy groups are condensed into a methylenedioxy bridge. This produces a fourth ring and a structure which resembles a hybrid of colchicine, podophyllotoxin, and steganacin. Cornigerine was somewhat more toxic than colchicine with L1210 murine leukemia cells and caused them to accumulate in metaphase arrest. Cornigerine resembled colchicine in its interactions with tubulin in vitro, and it was also somewhat more potent than colchicine in these drug-tubulin interactions. Cornigerine inhibited tubulin polymerization both with and without microtubule-associated proteins, inhibited the binding of radiolabeled colchicine to tubulin, and stimulated tubulin-dependent GTP hydrolysis. Indirect evidence suggested that the binding of cornigerine to tubulin is relatively slow and temperature-dependent, like the binding of colchicine to the protein.

Animals↗
PubMed1988

Rett syndrome: EEG presentation.

Rett syndrome, a degenerative neurological disorder of girls, has a classical presentation and typical EEG findings. The electroencephalograms (EEGs) of 7 girls whose records have been followed from the onset of symptoms to the age of 5 or more are presented. These findings are tabulated with the Clinical Staging System of Hagberg and Witt-Engerström (1986). The records show a progressive deterioration in background rhythms in waking and sleep. The abnormalities of the background activity may only become evident at 4-5 years of age or during stage 2--the Rapid Destructive Stage. The marked contrast between waking and sleep background may not occur until stage 3--the Pseudostationary Stage. In essence EEG changes appear to lag behind clinical symptomatology by 1-3 years. An unexpected, but frequent, abnormality was central spikes seen in 5 of 7 girls. They appeared to be age related and could be evoked by tactile stimulation in 2 patients. We hypothesize that the prominent 'hand washing' mannerism may be self-stimulating and related to the appearance of central spike discharges.

Apraxias↗
PubMed1988

Cerebrospinal fluid values for monoamine metabolites, gamma-aminobutyric acid, and other amino compounds in Rett syndrome.

We measured concentrations of 3-methoxy-4-hydroxy-phenylglycol, 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindoleacetic acid--the metabolites of noradrenaline, dopamine, and serotonin used as central neurotransmitters--in the cerebrospinal fluid (CSF) specimens of five girls with Rett syndrome. These patients met the clinical criteria for both inclusion and exclusion of the diagnosis of Rett syndrome. In contrast to previous reports, cerebral monoamine metabolites were present in normal concentrations in CSF. In addition, concentrations of gamma-aminobutyric acid and of a large number of other amino acids and related compounds were normal in the CSF of patients with the syndrome. We doubt that an underlying biochemical cause for this disorder has yet been discovered.

Adolescent↗
PubMed1988

Rett syndrome: clinical profile and EEG abnormalities.

We studied 7 children with Rett Syndrome, characterized by behavioral and motor abnormalities which superficially resemble infantile autism, and reviewed the records of 4 adults with the same symptoms. Clinical details are discussed. No abnormalities were found in analyses of amino acids and biogenic amine metabolites. EEG showed a clear pattern of chronological deterioration, with the pattern of marked waking/sleep background contrast appearing consistently only after 5 years of age. There was also a high incidence of spike discharges in the central (Rolandic) region. The clinical pattern of Rett Syndrome should be differentiated from the syndrome of autism.

Adolescent↗
PubMed1986

Blood serotonin concentrations and fenfluramine therapy in autistic children.

Whole-blood serotonin concentrations of 31 autistic children, aged 2 1/2 to 16 years, 10 non-autistic retarded children, and 18 children with Down syndrome were measured by a fluorometric method and compared with those of normal children of similar age range. No significant difference in the serotonin concentration per milliliter of whole blood or per 1000 platelets was found between groups for autistic, retarded, or normal children, but the values for those with Down syndrome were significantly lower. A double-blind cross-over study on the effect of fenfluramine versus placebo in seven autistic boys over a period of 8 months demonstrated a significant decrease in blood serotonin levels during the fenfluramine phase in all subjects. Slight improvements were found in short-term auditory memory and some measures of receptive language skills, particularly in children functioning at a high level. There was no significant change in global psychometric measurements of general intelligence during therapy. No adverse clinical effect was observed other than weight loss of 6% in one child. We conclude that fenfluramine may have some selective favorable effects on increasing attention in high-functioning autistic children. Blood serotonin concentration may be followed as an indication of drug compliance during fenfluramine therapy, but does not appear to reflect clinical efficacy.

Adolescent↗
PubMed1986

Speed of stress wave propagation in lung.

The speed of stress waves in the lung parenchyma was investigated to understand why, among all internal organs, the lung is the most easily injured when an animal is subjected to an impact loading. The speed of the sound is much less in the lung than that in other organs. To analyze the dynamic response of the lung to impact loading, it is necessary to know the speed of internal wave propagation. Excised lungs of the rabbit and the goat were impacted with water jet at dynamic pressure in the range of 7-35 kPa (1-5 psi) and surface velocity of 1-15 m/s. The stress wave was measured by pressure transducer. The distance between the point of impact and the sensor at another point on the far side of the lung and the transit time of the stress wave were measured. The wave speed in the goat lung was found to vary from 31.4 to 64.7 m/s when the transpulmonary pressure Pa-Ppl was varied from 0 to 20 cmH2O where Pa represents airway pressure and Ppl represents pleural pressure. In rabbit lung the wave speed varied from 16.5 to 36.9 m/s when Pa-Ppl was varied from 0 to 16 cmH2O. Using measured values of the bulk modulus, shear modulus, and density of the parenchyma, reasonable agreement between theoretical and experimental wave speeds were obtained.

Animals↗