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Biomedical subjects

M Hammond

Publications and source records attributed to M Hammond.

11 recordsLinked to original sources
PubMed1992

Learning and behavioral--emotional problems of children born preterm at second grade.

A longitudinal prospective study examined the question, "which child and family factors discriminate between children born preterm who are characterized by the presence or absence of learning or behavioral-emotional problems at second grade?" Assessments were completed during the child's hospital stay at birth, at 4, 8, and 24 months, and 8 years of age for 68 children born preterm and their mothers. Discriminant analyses identified the variables that statistically maximized the differentiation between two groups of children defined to exhibit or not exhibit school age problems. Three categories of discriminators were used in the analyses: infant status, family interactive quality, and family context. The three significant discriminators were variables from the family categories. The results of this study highlight the importance of understanding the presence or absence of school age problems from a multivariate model of development that takes into account the quality of the child's interactions within the family during early childhood and school age and the current stress levels in the family context.

Achievement↗
PubMed1992

In vitro antifungal activities and in vivo efficacies of 1,3-beta-D-glucan synthesis inhibitors L-671,329, L-646,991, tetrahydroechinocandin B, and L-687,781, a papulacandin.

The in vivo anti-Candida activities of 1,3-beta-D-glucan synthesis inhibitors L-671,329, L-646,991 (cilofungin), L-687,901 (tetrahydroechinocandin B), and L-687,781 (a papulacandin analog) were evaluated by utilizing a murine model of disseminated candidiasis that has enhanced susceptibility to Candida albicans but increased sensitivity for discriminating antifungal efficacy. DBA/2 mice were challenged intravenously with 1 x 10(4) to 5 x 10(4) CFU of C. albicans MY1055 per mouse. Compounds were administered intraperitoneally at concentrations ranging from 1.25 to 10 mg/kg of body weight twice daily for 4 days. At 6 h and 1, 2, 3, 4, 7, and 9 days after challenge, five mice per group were sacrificed and their kidneys were homogenized and plated for enumeration of Candida organisms (CFU per gram). Progressiveness of response trends and no-statistical-significance-of-trend doses were derived to rank compound efficacy. 1,3-beta-D-Glucan synthesis 50% inhibitory concentrations were determined by using a C. albicans (MY1208) membrane glucan assay. Candida and Cryptococcus neoformans MICs and minimal fungicidal concentrations were determined by broth microdilution. L-671,329, L-646,991, L-687,901, and L-687,781 showed similar 1,3-beta-D-glucan activities, with 50% inhibitory concentrations of 0.64, 1.30, 0.85, and 0.16 micrograms/ml, respectively. Data from in vitro antifungal susceptibility studies showed that L-671,329, L-646,991, and L-687,901 had similar MICs ranging from 0.5 to 1.0 micrograms/ml, while L-687,781 showed slightly higher MICs of 1.0 to 2.0 micrograms/ml for C. albicans MY1055. Lipopeptide compounds were ineffective against C. neoformans strains. Results from in vivo experiments comparing significant trend and progressiveness in response analyses indicated that L-671,329 and L-646,991 were equipotent but slightly less active than L-687-901, while L-687,781 was ineffective at 10 mg/kg. Fungicidal activities of L-671,329, L-646,991, and L-687,901 were observed in vivo, with significant reduction in Candida CFU per gram of kidneys compared with those in sham-treated mice at doses of > or = 2.5 mg/kg evident as early as 1 day after challenge.

Animals↗
PubMed1992

Antipneumocystis activity of water-soluble lipopeptide L-693,989 in rats.

Water-soluble lipopeptide L-693,989 was evaluated for its antipneumocystis activity in rats. Rats from colonies with latent Pneumocystis carinii infections were immunosuppressed with dexamethasone for 6 weeks to facilitate the development of acute P. carinii pneumonia (PCP). After 6 weeks, the rats were maintained on dexamethasone and were treated twice daily for 4 days with various concentrations of L-693,989. At a dose of 0.15 mg/kg of body weight, the compound effectively eliminated 90% of the cysts in 4 days. Trophozoite forms of P. carinii were still present in these animals, as determined by using a P. carinii-specific DNA probe. A 3-week therapy study showed that the trophozoite load did not expand during treatment and that the trophozoites already present at the initiation of therapy appeared to persist. This may be a consequence of the stage specificity of the compound for cyst development and the severe immunosuppressive effects of dexamethasone on rats. When evaluated as a daily parenteral prophylactic agent, L-693,989 was effective in preventing the development of both P. carinii cysts and trophozoites, demonstrating its potential for use in prophylaxis and implying that the cyst stage of P. carinii is an obligatory step in trophozoite multiplication. The foamy exudate commonly associated with P. carinii infections was absent in the lungs of rats on prophylaxis. The compound was also evaluated via oral administration and was found to have a 90% effective dose of 32 mg/kg for therapy of acute infections and 5 mg/kg for daily prophylaxis.

Animals↗
PubMed1992

Effects of hypoxemia at sea level and high altitude on sodium excretion and hormonal levels.

Acute hypoxemia at sea level is associated with decreased aldosterone secretion. This inhibition is thought to be mediated through secretion of atrial natriuretic factor (ANF). The interaction of these two hormones should result in enhanced renal salt excretion during hypoxemic conditions. This hypothesis was tested by administration of a standardized salt load to seven normal subjects during normoxemia at sea level (SL), acute hypoxemia (AH) at sea level, and high altitude (HA) (3,000 m). Urine and venous blood samples were collected and analyzed. A natriuresis and diuresis was observed only under AH conditions. It was accompanied by a decrease in plasma aldosterone levels, but did not correlate with changes in plasma aldosterone levels, ANF, or other hormones. Increased plasma renin activity (PRA) and increased norepinephrine levels were encountered at HA, suggesting sympathetic nervous system activation. No change in anti-diuretic hormone (ADH) levels with increased plasma osmolality was seen at HA. We conclude that excretion of a salt load during normobaric hypoxemia is enhanced by a decrease in plasma aldosterone levels, unrelated to changes in ANF or other hormones. The differences observed in norepinephrine, PRA, and ADH levels during HA versus AH conditions suggest that hypobaria or chronic hypoxemia may influence these hormonal responses.

Acute Disease↗
PubMed1991

HLA antigens in donovanosis (granuloma inguinale).

OBJECTIVE: To compare the frequencies of HLA antigens in patients with donovanosis and in controls. DESIGN: HLA Class I, Class II and DQ antigens were detected in patients with genital ulceration caused by donovanosis and in a control group. SETTING: City Health STD Clinic, King Edward VIII Hospital, Durban, South Africa. Participants--Sixty (47 men, 13 women) patients with donovanosis. RESULTS: HLA B57 was detected in nine of 60 (15%) with donovanosis and 75 of 1478 (5.1%) controls (RR = 3.3 chi 2 = 11.0, p = 0.001, p corrected = 0.026). CONCLUSIONS: A possible link between donovanosis and HLA B57 could be explained by coexisting alleles or immune response genes in linkage disequilibrium altering disease susceptibility.

Disease Susceptibility↗
PubMed1977

Extrathyroidal conversion of thyroxine to 3,3',5'-triiodothyronine (reverse-T3) and to 3,5,3'-triiodothyronine (T3) in humans.

In order to estimate the relative magnitude of the two alternative pathways of monodeiodination of thyroxine (T4) in adult humans, the metabolic clearance rates (MCR) and production rates (PR) of 3,3',5'-triiodothyronine (reverse-T3,rT3) and of 3,5,3'-triiodothyronine (T3) were determined in six euthyroid control subjects (C) and in five hypothyroid patients (H) receiving L-T4 as replacement therapy (0.15-0.3 mg/day). MCR was computed by a non-compartmental method of analysis from the plasma disappearance of 125I rT3 and 131I T3 during 72 h following simultaneous injection of tracers. PR was calculated from MCR and the serum concentration of rT3 and T3, respectively, determined by radioimmunoassay. In the H subjects, rT3 MCR averaged 97.1 +/- 12.8 (SD) 1/day and rT3 PR, 34.3 +/- 12.8 microng/day; T3 MCR was 28.7 +/- 6.1 1/day and T3 PR, 20.3 +/- 6.6 microng/day (all corrected to 70 kg body weight). These results were not significantly different from those in the control group; rT3 MCR 104 +/- 24 1/day, rT3 PR 33.0 +/- 9.2 microng/day; T3 MCR 24.0 +/- 5.9, T3 PR 24.2 +/- 4.1. The proportionof total triiodothyronine (rT3 averaged 62% in H patients and was similar (57%) in the C group. The results obtained in the H subjects indicate that the production of rT3 is a major route of T4 metabolism, equal to or exceeding that of T3. From the close agreement between the mean values for rT3 PR in the C and H groups it is concluded that most, if not all of the rT3 produced in normal humans is derived by extrathyroidal conversion from T4.

Aged↗
PubMed1975

Effects of enucleation in retinal degenerate mice.

Two experiments are reported which examine the effects of optic enucleation upon behavior of retinal degenerate C3H/HeJ mice. Enucleation did not affect acquisition of a two-way avoidance task. However, enucleated mice were more active than unoperated controls. The increased activity was not specific to the avoidance task since it also occurred in the closed field. The enucleation-induced increase in closed field activity did not depend upon age at time of testing or postsurgical recovery time. Several alternative explanations are considered, including the possibility that some information may be processed by the eye in the absence of traditionally conceived photoreceptors.

Animals↗
PubMedDate not supplied

Empyema necessitatis: review of the manifestations of thoracic actinomycosis.

Actinomycosis is a relatively uncommon infectious process involving the chest. A case of thoracic actinomycosis mimicking an inflammatory breast carcinoma in an elderly woman is presented with a review of the literature. The authors suggest that considering this disease in the differential diagnosis of indolent pulmonary parenchymal and pleural lesions is essential if appropriate diagnostic tests are to be obtained and proper therapy initiated, thus avoiding unnecessary invasive procedures.

Actinomycosis↗