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Biomedical subjects

H Smith

Publications and source records attributed to H Smith.

At least 361 records · Page 20Linked to original sources
PubMed1987

Aspergillus nidulans beta-tubulin genes are unusually divergent.

Aspergillus nidulans has two beta-tubulin genes: benA, which is involved in both vegetative growth and asexual sporulation, and tubC, which is involved mainly in asexual sporulation. Both genes have now been cloned and sequenced. benA encodes a polypeptide of 447 amino acids (aa) and tubC encodes one of 449 aa. The two polypeptides differ by 78 aa residues but the net charge for the two proteins remains the same. The divergence between the amino acid sequences of the Aspergillus beta-tubulins is greater than that for any other two beta-tubulins yet described in the same organism. The benA gene has eight introns and the tubC gene has five, all of which correspond in amino acid position to introns in benA. The positions of some of these introns are conserved in other beta-tubulin genes. The 5'-splice site, internal, and 3'-splice site consensus sequences are similar to those found in other fungal introns. The transcriptional start points for each gene have been determined using primer extension and/or S1 nuclease mapping. Neither the benA gene nor the tubC gene contains a TATA sequence in its 5'-flanking region. The tubC gene has two repeated upstream sequences which are not found in benA. The sites of polyadenylation have been determined for each gene using S1 nuclease mapping. Neither gene contains a polyadenylation signal, AATAAA, typical of other eukaryotic genes.

Amino Acid Sequence↗
PubMed1987

Differential production of endogenous pyrogen by human peripheral blood leucocytes following interaction with H3N2 or H1N1 influenza viruses of differing virulence.

Fever and other constitutional effects of influenza (headache, myalgia, listlessness, nausea, shivering, anorexia and depression) result from liberation of endogenous pyrogen (EP) from phagocytes. These effects are milder for recent H1N1 influenza virus isolates than for H3N2 strains. Interaction with human peripheral blood leucocytes in vitro showed that H1N1 strains, A/USSR/90/77 and A/Fiji/15899/83, elicited significantly less EP (as assessed by the rabbit pyrogen assay) than two virulent clones, 7a and 64c, of the A/Puerto Rico/8/34-A/England/939/69 (H3N2) reassortant virus system. Similar observations were made with UV-inactivated A/Fiji/15899/69 and clone 64c. These results are in accord with the differential severity of fever produced by these strains in ferrets when intranasally infected or intracardially inoculated with live and inactivated viruses. They show that influenza virus strains differ in capacity to induce EP from phagocytes. Furthermore, the observations with inactivated virus show that certain virion components are pyrogenic and differ in quantity or nature between strains. These results are important in relation to the differential severity of influenza epidemics and the reactogenicity of vaccine strains.

Animals↗
PubMed1987

Role of milk-derived IgG in passive maternal protection of neonatal ferrets against influenza.

Neonatal ferrets are protected against infection with influenza virus by colostral and milk-derived anti-influenza virus IgG after suckling on an immune mother. The levels of IgG elicited and then transmitted to neonates were similar when mothers were immunized by either live infection or killed vaccines. Maternal anti-influenza virus IgA and IgM appears not to cross the neonatal gut epithelium although both are present in maternal serum and milk.

Animals↗
PubMed1987

Rapid phytochrome regulation of wheat seedling extension: light pretreatment extends coupling time, increases response lag, and decreases light sensitivity.

Rapid effects of light on wheat seedling extension growth were monitored by sensitive transducer techniques. Seedlings grown in complete darkness responded to light by a marked deceleration of extension growth after a mean latent period of 10.4 minutes. Pulses (5 minutes) of red (660 nanometers), green (530 nanometers), and far-red (730 nanometers) light caused marked extension rate depression, and the red effect could not be reversed by 730 nanometers far-red. Pulses of 1 second red (72 micromoles per square meter) were effective, and were reversible by immediate long wavelength (759 nanometers) far-red. Seedlings pretreated with 2 minute broadband green light (0.6 micromole per square meter), 28 hours prior to the experimental light treatments, displayed similar extension rate decelerations in response to red light, but after a longer mean lag of 23.75 minutes. No response was observed with red light treatments of less than 1 minute, and the effects of 5 minutes of red light were fully reversible by 5 minutes of 730 nanometers far-red. Fluence-response curves showed that nonpretreated seedlings were approximately 100 times more sensitive to far-red-absorbing form of phytochrome than were those given prior light treatment. Although the fluence-response relationship for nonpretreated seedlings matched the photoconversion kinetics of phytochrome reasonably well, that for the pretreated seedlings indicated a requirement for repeated photoconversions for maximum action. The results are discussed in relation to the possibility that phytochrome may regulate the availability, or the activity, of a component of its own transduction chain.

Journal Article↗
PubMed1987

Clinical evaluation of a two-site immunoradiometric assay for adrenocorticotrophin in unextracted human plasma using monoclonal antibodies.

We have developed a sensitive two-site immunoradiometric assay (IRMA) for intact ACTH and its precursors, pro-opiomelanocortin and 22 kDa peptide in unextracted human plasma. The assay uses two monoclonal antibodies. Antibody 1A12, specific for ACTH 10-18, is radiolabelled and antibody 2A3 specific for the C-terminal region (ACTH 24-39), is coupled to Sephacryl S300 for the solid-phase. Samples are incubated for 18 h with labelled antibody followed by 2 h with solid-phase antibody. Separation employs the sucrose layering technique. Using human pituitary ACTH 1-39 (code 74/555) in diluent containing 10% horse serum to standardize the assay, the sensitivity (upper 99% confidence limit of zero standard) is 3.5 +/- 0.8 ng/l (n - 7). The mean coefficient of variation is 5.9% within-assay and 6.7% between-assay and is less than 10% between 22 and greater than 5000 ng/l. Mean recovery of ACTH 1-39 added to dexamethasone-suppressed human plasma is 109% and endogenous ACTH behaves indistinguishably from standard ACTH on dilution. In normal subjects, mean plasma ACTH levels are 30 ng/l at 0730 h, and 15 ng/l at 1630 h at rest. ACTH concentrations are between 60 and 330 ng/l, 8-10.5 h after metyrapone (2 g orally at 2300 h), between 140 and 320 ng/l, 30-60 min after insulin-induced hypoglycaemia, and less than 4 ng/l, 8 h after dexamethasone (1.5 mg orally at 2300 h). In a range of pathological conditions ACTH concentrations accurately reflect the disorders of the pituitary-adrenal axis. Endogenous ACTH immunoactivity is stable in vitro at 22 degrees C for at least 1 h in whole blood and at least 4 h in plasma. It is concluded that this two-site IRMA for ACTH in unextracted plasma offers a reliable assay for clinical purposes.

Adrenal Gland Diseases↗
PubMed1987

Construction and use of signal sequence selection vectors in Escherichia coli and Bacillus subtilis.

To study the diversity and efficiency of signal peptides for secreted proteins in gram-positive bacteria, two plasmid vectors were constructed which were used to probe for export signal-coding regions in Bacillus subtilis. The vectors contained genes coding for extracellular proteins (the alpha-amylase gene from Bacillus licheniformis and the beta-lactamase gene from Escherichia coli) which lacked a functional signal sequence. By shotgun cloning of restriction fragments from B. subtilis chromosomal DNA, a great variety of different export-coding regions were selected. These regions were functional both in B. subtilis and in E. coli. In a number of cases where protein export had been restored, intracellular precursor proteins of increased size could be detected, which upon translocation across the cellular membrane were processed to mature products. The high frequency with which export signal-coding regions were obtained suggests that, in addition to natural signal sequences, many randomly cloned sequences can function as export signal.

Bacillus subtilis↗
PubMed1987

Airway hyper-reactivity and eosinophilia in rats treated with Sephadex particles.

The intravenous injection of Sephadex particles (G200) into rats produced a specific increase in numbers of blood eosinophils, peaking 7 days later. A second injection, given on day 14 when the numbers of blood eosinophils had fallen to control levels, produced a dose-dependent increase in numbers, greater than the first, and peaking 5 days later. At this time, there was a dose-dependent increase in numbers of eosinophils, but not of other leucocytes, in broncho-alveolar lavage fluids and lung tissue, together with an increase in sensitivity of the rats to the respiratory effects produced by the intravenous injection of 5-hydroxytryptamine.

Animals↗
PubMed1987

Clinical features of covert toxocariasis.

The clinical features found in 14 children with toxocara ELISA titres of greater than or equal to 0.7 were compared with those found in 34 toxocara negative children. Blood eosinophils were elevated in 7 of the 14 patients and the highest eosinophilia was 14%. There was a highly significant association between hepatomegaly, cough, sleep disturbance and a raised titre (p less than 0.01). Behaviour disturbance, abdominal pain and headache were also significantly associated with a raised titre (p less than 0.05). The combination of abdominal pain, headache and cough was even more significantly associated with a high titre (p less than 0.0005) than were individual clinical features. It is suggested that in addition to the two well recognised clinical conditions of visceral larva migrans and ocular toxocariasis the clinical entity of covert toxocariasis should receive recognition. Eosinophilia may or may not be present in this condition.

Abdomen↗
PubMed1987

Histiocytosis-X isolated to the cervical spinal cord.

Histiocytosis-X may involve many tissues, including the central nervous system. This report is the first documentation of histiocytosis-X occurring exclusively in the spinal cord. We present a patient with cervical spinal cord disease causing spastic paraplegia, flaccid right arm weakness, and sensory loss. Magnetic resonance imaging of the spinal cord clearly demonstrated the entire lesion. Following surgical decompression and biopsy, the cervical spinal cord was treated with low-dose radiation, which resulted in complete regression of the lesion by radiologic assessment. The child became neurologically normal, and histiocytosis-X has not been detected in other organ systems.

Histiocytosis, Langerhans-Cell↗
PubMed1987

Production of passive immunity in neonatal ferrets following maternal vaccination with killed influenza A virus vaccines.

Neonatal ferrets may be passively immunized following maternal vaccination with formalin-inactivated influenza A virus vaccine, but the level of protection from partial to complete depends upon the number of doses used to vaccinate the mother, the presence or absence of aluminum hydroxide adjuvant, whether or not the mothers were 'primed' by prior infection with a serologically heterologous type A virus, and the age of the neonate at challenge. Neonates were completely protected up to 2 weeks of age, but susceptibility returned to nasal epithelium at 5 weeks and to lung at 7 weeks. Mothers immunized up to 9 months previously also partially or completely protected their offspring, this correlating with the maternal serum haemagglutination-inhibition (HI) antibody titre at the time of neonatal challenge, not the duration of immunity.

Adjuvants, Immunologic↗
PubMed1986

Cerebral astrocytoma as a complication of acute lymphoblastic leukaemia.

A boy who developed acute lymphoblastic leukaemia at the age of two years and 10 months had several central nervous system relapses, and received two courses of cranial irradiation, each of 24 Gy, in addition to systemic and intrathecal chemotherapy. Nearly 10 years after the onset of his leukaemia he developed a brain stem astrocytoma from which he died. This appears to be a rare occurrence, and the role of the treatment in the induction of his second tumour is discussed. The need for the long-term follow-up of cancer patients after apparent cure is emphasized.

Astrocytoma↗
PubMed1986

Molecular cloning of two cysteine proteinases from paw-paw (Carica papaya).

Two cDNA clones for plant cysteine proteinases have been isolated from a Carica papaya (paw-paw, papaya) leaf tissue cDNA library by using a mixture of 16 synthetic oligodeoxyribonucleotides as a hybridization probe. The inserted regions are 311 and 440 base-pairs in length and have the potential to encode a region corresponding to the C-terminal region of two proteins which are homologous with the known plant cysteine proteinases and the mammalian thiol cathepsins. One of the sequences shows a high (greater than 77%) homology with the plant cysteine proteinase papain, the other is closely related to papaya chymopapain. One sequence contains all, and the other most, of the 3' untranslated region of the mRNA. The inserts were used as specific probes in Northern Blot analyses giving an estimated size for the two mRNA species of 1.45 kilobases.

Amino Acid Sequence↗
PubMed1986

Selection and optimisation of monoclonal antibodies for a two-site immunoradiometric assay for ACTH.

Four monoclonal antibodies with predominant specificities towards different sequences within the ACTH molecule were investigated in a 2-site immunoradiometric assay (IRMA) for human ACTH. Antibody 3H9 recognises the extreme N-terminal sequence, antibodies 1A12 and 1D1 are specific for the mid N-terminal sequence but differ in that the former cross-reacts with alpha MSH whereas the latter does not, and antibody 2A3 recognises the C-terminal sequence. Combinations of iodinated antibodies with antibodies covalently linked to Sephacryl S300 were tested for their compatibility and potential for a sensitive assay. Two antibody combinations (1D1 plus 3H9 or 1A12) gave no dose-response curve indicating severe steric inhibition, whereas other combinations yielded assays with widely different detection limits (2-2400 ng ACTH/l). The combination of labelled 1D1 and solid-phase 2A3 gave the most sensitive assay and when optimised for antibody concentrations and incubation times the working range was 10-5 X 10(4) ng/l (CV less than 20%). The optimised sequential 2-step IRMA involves incubation of standard or test sample with labelled 1D1 for 18 h at 4 degrees C followed by incubation with solid-phase 2A3 for 2 h at room temperature, after which the labelled complex is separated by the sucrose layering technique. The detection limit of this IRMA was several 100-fold lower than by RIA using the same antibodies. The IRMA detected large molecular weight precursors containing the full ACTH sequence (22 000, 31 000 and 34 000) but not ACTH fragments (1-18, 1-24, 18-39). It is concluded that selected monoclonal antibodies provide a sensitive and rapid 2-site IRMA for intact ACTH and its precursors.

Adrenocorticotropic Hormone↗
PubMed1986

Radial keratotomy and glare effects on contrast sensitivity.

After radial keratotomy (RK) to correct myopia, some patients complain of 'glare'. Effects of a glare source on contrast sensitivity were measured in fifteen patients after unilateral RK. With each eye, determinations were made of the contrast required for detection of steady gratings (spatial frequencies of 0.7 and 2.9 cycles/deg), and for detection of flicker (unpatterned field flickering at rates of 8, 16, and 32 Hz). Grating or flicker was presented on a centrally fixated 4 deg test target (34 cd/m2 mean luminance), surrounded by a diffuse glare source (1700 cd/m2 mean luminance). For each stimulus, contrast thresholds were determined with glare-source off and with glare-source on. 'Glare loss' was defined as the decrement in contrast sensitivity measured with the glare source on. Significant findings were: (1) Both eyes showed glare losses for detection of gratings and for detection of flicker; (2) Spectacle lenses increased glare losses both for gratings and for flicker; (3) The RK eye showed a larger glare loss for flicker than the unoperated eye, but a smaller glare-loss for gratings; (4) For both flicker and gratings, glare loss tended to be greater in the RK eye, compared to the unoperated eye, in subjects who had larger pupil diameters in the testing situation; (5) The psychophysical measurements obtained in this study were not significantly correlated either with a questionnaire index of glare complaints or with the score obtained with the Miller-Nadler GlareTester.

Adult↗
PubMed1986

Impact of associated medical conditions on clinical features of gout.

In view of the various available drugs, we are now in a very much better situation for treatment of gout, with and without associated medical conditions. When several drugs are employed in one single patient, however, one may run into drug interactions, resulting into exaggerated hyperuricemia or induced acute gouty arthritis. In lieu of the various associated medical conditions, controlled or uncontrolled, the clinical features of gout may be modified. Accordingly, one must treat the patient's gout as well as his various stages of the associated medical conditions, and each patient must be individualized.

Adult↗