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Biomedical subjects

M C White

Publications and source records attributed to M C White.

At least 163 records · Page 9Linked to original sources
PubMed1981

Metal Complexation in Xylem Fluid : III. ELECTROPHORETIC EVIDENCE.

The capacity of ligands in xylem fluid to form metal complexes was tested with a series of in vitro experiments using paper electrophoresis and radiographs. The xylem fluid was collected hourly for 8 hours from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. Metal complexation was assayed by anodic or reduced cathodic movement of radionuclides ((63)Ni, (65)Zn, (109)Cd, (54)Mn) that were presumed to have formed negatively charged complexes.Electrophoretic migration of Ni, Zn, Cd, and Mn added to xylem exudate and spotted on KCl- or KNO(3)-wetted paper showed that stable Ni, Zn, and Cd metal complexes were formed by exudate ligands. No anodic Mn complexes were observed in this test system. Solution pH, plant species, exudate collection time, and Zn phytotoxicity all affected the amount of metal complex formed in exudate. As the pH increased, there was increased anodic metal movement. Soybean exudate generally bound more of each metal than did tomato exudate. Metal binding usually decreased with increasing exudate collection time, and less metal was bound by the high-Zn exudate.Ni, Zn, Cd, and Mn in exudate added to exudate-wetted paper demonstrated the effect of ligand concentration on stable metal complex formation. Complexes for each metal were demonstratable with this method. Cathodic metal movement increased with time of exudate collection, and it was greater in the high-Zn exudate than in the normal-Zn exudate. A model study illustrated the effect of ligand concentration on metal complex stability in the electrophoretic field. Higher ligand (citric acid) concentrations increased the stability for all metals tested.

Journal Article↗
PubMed1981

Gonadotrophin levels in women with Cushing's syndrome before and after treatment.

Basal serum concentrations of LH and FSH and their response to LHRH were studied in twelve pre- and ten post-menopausal women with Cushing's syndrome before and after treatment. Subnormal basal concentrations of LH were found in twelve out of twenty-two, and of FSH in ten of the twenty untreated patients. There was a correlation between the urinary free cortisol (UFC) and basal LH values, r = -0.59 (P less than 0.05), and UFC and basal FSH values, r = -0.76 (P less than 0.02) in the premenopausal women. All seven patients with a UFC value greater than 1080 nmol/24 h (normal range less than 270) had both a subnormal basal gonadotrophin level and a subnormal response of at least one gonadotrophin to the releasing hormone. In those patients in whom successful remission was obtained and who did not require replacement therapy, subnormal basal gonadotrophins were usually restored towards or into the normal range. It is concluded that while gonadotrophin levels may be normal in women with Cushing's syndrome, they are subnormal in those with the highest cortisol values. This may be due to a direct suppressive effect of cortisol on the release of stored pituitary hormone, and/or on LHRH release from the hypothalamus.

Adult↗
PubMed1981

Bromocriptine suppresses ACTH secretion from human pituitary tumour cells in culture by a dopaminergic mechanism.

Bromocriptine (0.13-13 microM) significantly inhibited ACTH secretion in a dose-dependent manner when added to cell cultures of a human corticotrophic adenoma for 24 h. Haloperidol (13 microM), but not serotonin (13 microM), blocked this inhibition but had no significant effect when added alone. In addition, dopamine (10 microM) reduced ACTH secretion during a 4-h incubation, whereas serotonin (0.01-10 microM) was ineffective. An ectopic ACTH secreting lung carcinoid was non-responsive to doses of bromocriptine up to 13 microM. These results demonstrate a direct suppressive action of bromocriptine on a human pituitary corticotrophic adenoma through dopaminergic rather than serotoninergic mechanisms.

Adenoma↗
PubMed1981

Reversal of diabetic retinopathy by continuous subcutaneous insulin infusion: a case report.

We report the case history of a 20-year-old diabetic girl with long-standing poorly controlled disease who presented with severe retinopathic features and who was treated with continuous subcutaneous insulin infusion (CSII). When first seen she had macular oedema and a visual acuity of 6/18 in her only eye, together with multiple blot haemorrhages and intraretinal microvascular abnormalities. Marked reversal of the retinal lesions occurred within 65 days of initiating SCII and after only 36 days of constant normoglycaemia. Subsequent good blood glucose control on conventional subcutaneous insulin injections has been achieved, and the retinopathy remains quiescent with a visual acuity of 6/5. We suggest that CSII may be a potentially useful method of arresting and reversing early diabetic retinopathy.

Adult↗
PubMed1981

24-Hour studies of prolactin and growth hormone levels in diabetic impotence.

Serum prolactin and growth hormone levels were measured hourly over 24 h in 8 insulin-treated diabetic males, 4 of whom were impotent. All patients showed normal sleep-related peaks of both hormones during the night. The mean 24-hour concentrations of prolactin and growth hormone were similar in patients with impotence (9.4 +/- 1.0 ng/ml and 3.8 +/- 0.4 microIU/ml, respectively) and without it (10.5 +/- 1.0 ng/ml and 4.7 +/- 1.1 microIU/ml, respectively). The mean prolactin and growth hormone concentration during the day time (7.00 a.m. to 7.00 p.m.) and the night time (7.00 p.m. to 7.00 a.m.) were also similar in patients with and without impotence. These results suggest that impotence in diabetic patients is not mediated by abnormalities of prolactin and growth hormone secretion.

Adult↗
PubMed1981

Plasma pyridostigmine levels in myasthenia gravis.

Plasma concentrations of pyridostigmine were measured after oral administration in 16 patients with myasthenia gravis. The levels varied greatly among both well- and poorly controlled patients, but were usually higher in the latter group. Absorption of the drug appears to be erratic; its clearance from the plasma is slow and its metabolism could involve an enterohepatic circulation. Drugs such as methylcellulose may prevent absorption. Three poorly controlled patients were studied on a high-dose alternate-day steroid regimen, and a marked decrease in pyridostigmine bioavailability on the same dose of drug was observed in all three. No such changes were demonstrated in a volunteer group taking a lower dose of steroids.

Biological Availability↗
PubMed1980

Risk factors for toxocaral ocular larva migrans: a case-control study.

Twenty-four patients with serologically confirmed toxocaral ocular larva migrans (OLM) and 24 age- and sex-matched controls were the subjects of an epidemiologic study. Information on the exposure to dogs and other factors possibly associated with transmission of toxocariasis was obtained by contacting the parents of the subjects. The odds of having had a dog present in the household within the year previous to onset of illness were 3 to 1 for cases vs controls. An association of pups (< 3 months) in the households of OLM patients within one year of onset was statistically significant (P < .05). Twenty-three of 24 OLM patients had had dogs in their homes some time before their illness, and the twenty-fourth patient had a history of geophagia, a behavioral pattern previously identified as a risk factor for toxocariasis. Exposure to cats and other animals in or outside the home did not differ for patients and controls. Infected dogs, especially pups, in the patients' homes were the most probably sources of infection for this group of OLM patients.

Adolescent↗
PubMed1979

Long-term continuous subcutaneous insulin infusion in diabetics at home.

6 insulin-requiring diabetics were treated at home with continuous, long-term, dual-rate subcutaneous insulin infusion (CSII) by means of a portable syringe pump. The duration of infusion was 48--111 days. Patients were initially stabilised on CSII in hospital and then allowed home, where capillary-blood glucose control was monitored by the patients with glucose-oxidase reagent strips. Patients diluted and changed their own insulin for the pump, adjusting the dose according to the control achieved. Mean (+/- SD) blood-glucose values ranged from 4.8 +/- 1.6 to 7.5 +/- 1.6 mmol/l. In 1 longstanding diabetic insulin requirements fell from 92 U/day to about 35 U/day on CSII. 2 newly diagnosed juvenile-onset diabetics were also infused: in 1 patient requirements fell to zero after 48 days and in the other the dose fell to 14 J/day after 51 days of CSII. No cannula-site infection or significant palpable lipodystrophy was experienced. Patients treated with "open-loop" systems have little or no insulin reserve: potential loss of control--for example, during intercurrent illness-demands careful metabolic monitoring and prompt correction.

Adolescent↗
PubMed1977

An assessment of the possible association of isoniazid with human cancer deaths.

The data from 2 U. S. Public Health Service trials of isoniazid preventive therapy were reviewed in an effort to evaluate the risk of death from cancer among persons who received such therapy. Each of these prospective trials used random assignment to either isoniazid or placebo. More than 25,000 persons participated in each of the trials. The length of follow-up ranged from 10 to 14 years in one trial and from 9 to 11 years in the other. No significant difference in the incidence of death from cancer was noted between groups treated with placebo or with isoniazid in either of the studies. This was true even when deaths due to specific types of cancer and age-specific cancer death rates were compared. These data do not support a carcinogenic effect of isoniazid in humans.

Adolescent↗
PubMedDate not supplied

Exposure to methyl tertiary-butyl ether from oxygenated gasoline in Stamford, Connecticut.

In 1993, state health officials in Connecticut invited the Centers for Disease Control and Prevention (CDC) to assist in an investigation of exposure to methyl tertiary-butyl ether in oxygenated gasoline in Stamford, Connecticut. Venous blood samples were collected from 14 commuters and from 30 other persons who worked in the vicinity of traffic or automobiles, and the samples were analyzed for methyl tertiary-butyl ether, tertiary-butyl alcohol, benzene, m-/p-xylene, o-xylene, and toluene. The highest levels of methyl tertiary-butyl ether in blood were measured among gasoline service station attendants (median = 15 micrograms/l, range = 7.6-28.9 micrograms/l). Blood levels of methyl tertiary-butyl ether were highly variable among persons who worked in car-repair shops (median = 1.73 micrograms/l, range = 0.17-36.7 micrograms/l) and were generally lowest among commuters (median = 0.11 micrograms/l, range = < 0.05-2.60 micrograms/l). Blood levels of methyl tertiary-butyl ether were correlated strongly with personal-breathing-zone samples of methyl tertiary-butyl ether and blood levels of other volatile organic compounds. This exposure information should prove useful to a future risk analysis of this high-volume chemical.

Air Pollutants↗
PubMedDate not supplied

Comparison of the immunogenicity of hepatitis B vaccine administered intradermally and intramuscularly.

Although hepatitis B vaccine reliably induces immunity to hepatitis B virus, the expense of intramuscular (im) vaccination with this product has limited its use. To determine if a smaller, less expensive, intradermal (id) dose of hepatitis B vaccine would be an effective alternative, we compared the response of antibody to hepatitis B surface antigen (anti-HBs) following im vaccination to that following id vaccination. Volunteers who were seronegative for antibody to hepatitis B core antigen were enrolled in the study and received either im or id vaccine. A total of 108 subjects received three 1-mL im injections of hepatitis B vaccine, and another 110 subjects received four 0.1-mL id injections of the vaccine. Similar rates of seroconversion occurred; greater than or equal to 10 mIU of anti-HBs/mL was noted following either three im or three id vaccinations. Furthermore, 2 years after initiation of vaccination, the serum concentration of anti-HBs for id vaccine recipients was similar to that for im vaccine recipients.

Adult↗