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C Smith

Publications and source records attributed to C Smith.

At least 955 records · Page 53Linked to original sources
PubMed1983

Biological activity of 24,24-difluoro-25-hydroxycholecalciferol in chicks.

The biological activity of subcutaneously injected 24,24-difluoro-25-hydroxycholecalciferol was compared with that of 25-hydroxycholecalciferol in the vitamin D-deficient growing chick. 24,24-Difluoro-25-hydroxycholecalciferol is equal to 25-hydroxycholecalciferol in the stimulation of: 1) growth, 2) intestinal calcium absorption, 3) elevation of serum calcium and serum phosphorus, 4) healing of rachitic cartilage (radiography), and 5) mineralization of rachitic bone (bone ash). The response appears to be linear in the range of 13.0 to 325 pmol daily. Since 24,24-difluorocholecaliferol cannot be 24-hydroxylated to produce either 24,25-dihydroxycholecalciferol or 1,24,25-trihydroxycholecalciferol, while it can be 1 alpha-hydroxylated to produce 24,24-difluoro-1,25-dihydroxycholecalciferol, these results demonstrate that 24-hydroxylation is not required for the known functions of cholecalciferol in the chick.

Animals↗
PubMed1983

The kinin system and ovulation: changes in plasma kininogens, and in kinin-forming enzymes in the ovaries and blood of rats with 4-day estrous cycles.

Rats with 4-day estrous cycles showed a 51% fall in plasma kininogen in early proestrus (1200-1500). Levels remained depressed throughout ovulation, and then recovered steadily. The initial fall corresponded well with the LH surge. Initial attempts were made to detect enzymes which might be responsible for the change. Kinin-forming enzymes, in either precursor or active forms, were absent from the ovaries in diestrus, but appeared at the onset of the fall in kininogen (kinin-forming activity, 2.87 +/- 0.83 ng bradykinin (BK) equiv. X g wet tissue-1 X min-1). They rose 10-fold just before ovulation, and then declined rapidly. This major peak, and a corresponding one in plasma, may have reflected the presence of follicular proteases. Plasma kinin-forming enzymes showed no apparent change when the kininogen first declined. They then disappeared, suggesting a more delayed activation and destruction. It seems possible that LH induces kinin-forming enzymes in the ovaries, and induces a later activation of plasma enzymes, to produce kinins which may be involved in vascular and permeability changes important in ovulation, and perhaps concerned in the mechanisms of positive feed-back with the pituitary.

Animals↗
PubMed1983

Diabetes-associated endometrial disruption in the ketonuric, diabetic Chinese hamster.

The effects of the ketonuric-diabetic (KD) condition on uterine endometrial morphology were studied in the genetically diabetic Chinese hamster. All KD hamsters were matched for age, body weight and cyclic state with nondiabetic control animals. All KD hamsters were reproductively acyclic as compared to controls. The uterine epithelium of KD hamsters was devoid of surface microvilli, secretory activity, and exhibited a height reduction as compared to controls. The basal lamina underlying the luminal epithelium was 2-5 times as thick in the KD condition than control. The endometrial stroma was disrupted in the KD hamsters, with the endometrium composed of rounded cells surrounded by a thickened intercellular matrix. This was in marked contrast to the stroma of controls which consisted of an orderly array of fibroblasts and collagen fibers. Stromal vessels had a thickened basement membrane in diabetic animals. The results of this study indicate that epithelial and stromal disruption are associated with the KD state in the Chinese hamster and are probably causally associated with reproductive failure.

Animals↗
PubMed1983

Changes in plasma kininogen levels in rats before ovulation, and after treatment with luteinizing hormone and oestradiol-17 beta.

The pre-ovulatory fall in plasma kininogens in rats with 4 day oestrous cycles started between 12.00 and 15.00 h pro-oestrus, reached a maximum decline of 51% by 18.00 h pro-oestrus, and started to recover before ovulation. Because these changes appeared to correspond with the LH-surge, and to follow the peak in plasma oestradiol-17 beta levels, both of these hormones were tested for possible effects on plasma kininogens. Intracardiac injections of 110 IU of equine LH into dioestrous rats were followed by a decline of 30.8 +/- 6.7% in plasma kininogens, 6 h after injection (significant, P less than 0.01). Values were still depressed, but recovering, 12 h after treatment; the reduction was 21.3 +/- 5.8% (significant, P less than 0.01). Controls showed no decline. Injections of oestradiol-17 beta (1.0 micrograms/100 g body weight) produced no significant effects. It is suggested that the LH surge may be responsible, at least in part, for the decline in plasma kininogens seen before ovulation.

Animals↗
PubMed1983

Expected relative responses to selection for alternative measures of life cycle economic efficiency of pork production.

Relative genetic responses to selection for alternative measures of economic efficiency of pork production were examined. The analysis was based on results from a deterministic bio-economic model of lifecycle pork production. Alternative aggregate breeding values considered were based on cost (+)/unit of live weight or of carcass output lean for different production systems and for different breeding roles of the selected stocks. For cost/unit of lean, changes in leanness (or fatness) dominated the index. For cost/unit of live weight, however, no one trait dominated the index, and changes in growth and reproductive traits as well as the breeding role of the stock (purebred, maternal or paternal) were important in defining selection objectives. Management and production systems were less important than breeding role for cost/unit live weight output, except that importance of growth rate was increased by marketing at the mean weight reached at a fixed age rather than at a fixed weight irrespective of age. Implications of these results for goals and systems of pig improvement are discussed.

Adipose Tissue↗
PubMed1982

Off with the old.

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Curriculum↗
PubMed1982

Chemical hyperthyroidism: serum triiodothyronine levels in clinically euthyroid individuals treated with levothyroxine.

We have observed many patients treated with levothyroxine sodium who have elevated serum thyroxine (T4) levels but appear clinically euthyroid. Such patients generally have normal serum triiodothyronine (T3) values. A retrospective review at The Johns Hopkins Hospital, Baltimore, comparing the correlation of T3 and T4 values in levothyroxine-treated patients with that in patients not so treated was carried out from 1977 to 1979. Mean free thyroxine index (FTI) value in 104 levothyroxine-treated patients was 4.70 +/- 0.2 and mean T3 value was 177 +/- 9 ng/dL. In a group of 50 hyperthyroid patients, mean FTI value was 7.26. +/- 0.5, with a mean T3 value of 389 +/- 26 ng/dL. In 71 euthyroid patients, mean FTI value was 2.36 +/- 0.1, with a T3 value of 137 +/- 3 ng/dL. Computed ratios of T3 to FTI and T3 to T4 were significantly lower in the group treated with levothyroxine than in either the hyperthyroid or euthyroid nontreated groups. Levothyroxine-treated patients with high T4 levels but normal T3 levels were clinically euthyroid. Patients not treated with levothyroxine with similarly elevated T4 levels had elevated T3 levels and were clinically hyperthyroid. It is concluded that lower relative T3 levels in levothyroxine-treated patients may explain why these patients appear clinically euthyroid despite elevated T4 values. Serum T3 determination is the procedure of choice for evaluation of levothyroxine-treated individuals. Furthermore, an elevated FTI value in such an individual does not, in itself, dictate need to reduce dosage.

Drug Administration Schedule↗
PubMed1982

Ability of primary care physicians to make accurate ratings of psychiatric symptoms.

The ability of 45 family practice residents to make accurate ratings of psychiatric symptoms among their patients was assessed by comparing their ratings with the symptom levels of their patients as reported on a psychiatric screening questionnaire. The findings confirmed an earlier survey with experienced primary care physicians by showing that ability to make accurate ratings is partly determined by interview style, and partly by certain personality attributes. Self-confident, outgoing physicians with high academic ability tend to make more accurate assessments, as do those who display certain specified behaviors during their diagnostic interviews. The tendency to make many, or to avoid making psychiatric assessments ("bias") is shown to be determined by different factors from those that determine accuracy of the assessments.

Family Practice↗
PubMed1982

Morphometric evaluation of the hypothalamic-ovarian axis of the ketonuric, diabetic Chinese hamster: relationship to the reproductive cycle.

The relationship between diabetes and the morphological alterations which occur in hypothalamic and ovarian tissue was examined in the long-term, ketonuric-diabetic Chinese hamster. Matched diabetic and non-diabetic control hamsters were inspected daily for changes in the reproductive cycle by vaginal lavage. On dioestrus, animals were perfused, the hypothalamus and ovaries collected, prepared for microscopy and morphometrically analyzed. The nuclei in the medial basal hypothalamus of diabetic hamsters exhibited a decreased area (p less than 0.01) and neuronal population (p less than 0.05-0.01) compared with controls. The ovaries of the diabetic animals had a reduced follicular population (p less than or equal to 0.05) and an increased atresia rate (p less than or equal to 0.05) compared with controls. In addition, all diabetic hamsters were acyclic. In diabetic animals, the corpora luteal cells contained a reduced lipid content (p less than or equal to 0.001) which was possibly functionally related to a significant decline in serum progesterone levels (p less than or equal to 0.01). Based on these results it is suggested that the hypothalamic-ovarian axis is both morphologically and functionally impaired in the diabetic hamster.

Animals↗
PubMed1982

Depopulation of the ventromedial hypothalamic nucleus in the diabetic Chinese hamster.

The relationship between diabetes and the size, density and area of the ventromedial hypothalamic nucleus (VMH) was studied in the genetically diabetic Chinese hamster. Matched diabetic and non-diabetic control chinese hamsters were perfused, the hypothalamus collected, sectioned and stained for light microscopy. The mid-point of each VMH nucleus was located, photographed and enlarged for morphometric analysis. Each neuron that possessed a nucleolus and was located within the confines of a VMH was counted, and subsequently the area of each nucleus and the density of neurons per area of VMH were calculated. The results indicated that both the area and absolute number of neurons within the VMH of diabetic hamsters were significantly reduced compared to control values (P less than 0.01) The density of neurons per unit area of VMH was similar in both groups. These data suggest that the VMH experiences a neuronal depopulation in diabetic hamsters which may have a functional influence on the hypothalamic-pancreatic axis in this species.

Animals↗