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Biomedical subjects

J F Nelson

Publications and source records attributed to J F Nelson.

At least 73 records · Page 4Linked to original sources
PubMed1984

Midline "nonhealing" granuloma.

Destructive processes of the midface can occur in a wide variety of diseases. Intrinsic in consideration of these is a cluster of lesions, including Wegener's granulomatosis (WG), idiopathic midline granuloma (IMG), polymorphic reticulosis (PR), and lymphoma. Although there is still confusion as to whether the latter three represent a spectrum of the same malignant process, there is general agreement that WG is a separate entity on the basis of clinical presentation and therapeutic response. It is probable that PR is an emergent lymphoma, with the same prognostic and therapeutic features. Idiopathic midline granuloma is clinically similar to PR and lymphoma, but histologically it appears to be inflammatory in nature with no clearly definable malignant cell type present. At this point in time three diseases are best collectively referred to as midline "nonhealing" granuloma. The cases presented represent the spectrum of this enigmatic process.

Adult↗
PubMed1984

A clinical comparison of speed group D and E dental x-ray films.

This study was conducted to determine the clinical diagnostic quality of the new higher-speed Ektaspeed E x-ray films when compared with the diagnostic quality of the lower-speed Ultraspeed D x-ray films. The study also attempted to determine the advantages of 70 versus 90 kVp. The results indicated that the E film at 90 kVp was slightly better than the E film at 70 kVp and the D films at either 70 or 90 kVp. Although the differences were statistically significant, average rating for all films fell within the range of acceptability.

Evaluation Studies as Topic↗
PubMed1984

Longitudinal studies of estrous cyclicity in aging C57BL/6J mice: II. Cessation of cyclicity and the duration of persistent vaginal cornification.

The of onset of acyclicity and the duration of persistent vaginal cornification (PVC), the predominant postcyclic anovulatory condition, were measured in five cohorts of virgin mice staggered across a 6-yr interval. The average age of cessation of cyclicity varied significantly among cohorts, ranging from 11 to 16 mo of age. Seventy-five percent of the mice entered PVC after ceasing to cycle, the remainder entered directly into a persistent diestrous condition. The duration of PVC, which averaged between 2 and 4 mo, varied markedly among individuals and was inversely related to the age of onset of acyclicity. Consequently, the variance associated with the cessation of cyclicity was about 4-fold greater than that associated with the cessation of PVC. These differing variances suggest that the factors governing ovulatory failure and PVC cessation may differ.

Aging↗
PubMed1984

Handling of phosphate by a parotid gland (ovine).

The handling of phosphate by the sheep's parotid gland was investigated by examining the effects on the composition of saliva of phosphate depletion, secretomotor nerve stimulation, enrichment of phosphate in the blood supply, and parotid arterial infusion of parathyroid hormone (PTH) and calcitonin. Experiments were performed in anesthetized sheep after vascular isolation of the parotid gland. In phosphate depletion arterial plasma phosphate fell from 1.50 +/- 0.12 to 0.73 +/- 0.08 mM. In phosphate repletion salivary phosphate ion was concentrated 8- and 16-fold compared with parotid arterial and venous plasma, respectively. In depletion salivary phosphate concentration was unchanged at slow salivary flow rate but was significantly lower at high flow rate. Enrichment of phosphate in the arterial blood increased salivary phosphate concentration in both situations. Synthetic bPTH (1-34), highly purified bPTH (1-84), and bovine parathyroid extract were equipotent in increasing salivary phosphate concentration in phosphate repletion and had no effect in phosphate depletion. They also increased parotid blood flow. The rise in phosphate with PTH was conditional on the rise in blood flow, but the same rise in blood flow alone did not reproduce the effect of PTH on salivary phosphate. PTH increased work done and oxygen consumption by the gland but arterial phosphate enrichment did not. Increases in salivary phosphate were associated with decreases in salivary bicarbonate, and the sum [HCO-3] + [Cl-] + (HPO2-4] remained almost constant. Micropuncture studies have shown that ovine parotid ducts do not normally reabsorb phosphate and therefore PTH probably increases phosphate secretion in the endpieces.

Animals↗
PubMed1984

Ovarian and steroidal influences on neuroendocrine aging processes in female rodents.

Some Mammalian aging processes involve effects of steroids on the brain and pituitary. An ovary-dependent, neuroendocrine aging syndrome of laboratory rats and mice is described in this article. This syndrome can be attenuated during aging by chronic ovariectomy and can be prematurely induced in young rodents by sustained exposure to estradiol (E2). The limited follicular stock in the ovary is proposed to be a major pacemaker of aging in this neuroendocrine syndrome; ovarian aging may interact with neuroendocrine aging. Ovary-independent neuroendocrine changes occur as well. We also discuss developmental influences on adult aging in rodents and other examples in which adult lower mammals are sensitive to long lasting effects of steroids on the brain and pituitary. Possible molecular mechanisms are considered. In view of the long lasting effects of E2 and other steroids on lower mammals, the potential for long term effects of ovarian steroids on the human brain and pituitary warrants continued evaluation.

Aging↗
PubMed1984

Evaluation of the biological properties of parathyroid hormone and analogues in a vascularly isolated parotid gland-based assay.

Infusion of bovine parathyroid hormone (bPTH) preparations into the arterial blood supply of the vascularly isolated parotid gland in anaesthetized sheep increases salivary phosphate concentration and gland blood flow rate with rapid onset and offset of action. These responses have been used as a bioassay for PTH and PTH analogues and for assessing the properties of an in-vitro inhibitory analogue [Nle-8, Nle-18, Tyr-34]bPTH-(3-34)amide. [Nle-8, Nle-18, Tyr-34]bPTH-(1-34)amide at 10(-9) to 10(-8) mol/l was four to five times more potent than bPTH(1-34) on both salivary phosphate and blood flow assays. Human PTH(1-34) was not significantly more potent than bPTH(1-34). The [Nle-8, Nle-18, Tyr-34]bPTH-(3-34)amide analogue had very slight agonist activity at 3 X 10(-7) mol/l and at a 100:1 ratio of analogue to PTH it completely inhibited the action of bPTH(1-34) on phosphate secretion and gland blood flow. It caused partial inhibition at 10:1 and had no evident effect at 1:1. These results differ from previous in-vitro results and indicate that the preparation may be valuable for evaluation of agonist and antagonist analogues of PTH. The vascularly isolated parotid gland of the sheep permits repeated random testing of analogues in a control-test-control sequence and the results indicate high sensitivity to PTH in a rapidly reactive in-vivo system with two responding parameters.

Animals↗
PubMed1984

Species differences in the effect of decreased CSF sodium concentration on salt appetite.

During the course of evolution from the beginning of the Caenozoic period, the mammalian species have irradiated into increasingly diverse environments and these physical conditions have imposed powerful selection pressures on the systems of water and salt homeostasis. In the case of physiological actions of hormonal elements of the control systems, effects of antidiuretic hormone and aldosterone on water and salt conservation and of renin-angiotensin II on blood pressure and aldosterone secretion show a general similarity across mammalian species. However, evidence is accruing that there may be large species variation in the vectors of physical, chemical and hormonal changes of the milieu which cause water and salt intake. In the sheep, physiological degree of reduction of CSF [Na] produced by IVT infusion of various hypertonic or isotonic saccharide solutions has a powerful stimulating effect on salt appetite of both Na replete and Na deficient animals. Increasing CSF [Na] reduces appetite. The 0.7 M mannitol CSF infusions initially stimulated thirst but eventually depressed it, presumably due to reduction of CSF [Na]. By contrast, in wild rabbits infusion of 0.9 M mannitol CSF for 2 days at 17 microliter/h caused a large reduction of water intake, a diuresis and no significant increase in salt intake. In laboratory white rats, 0.7 M mannitol CSF infusion at 10 microliter/h for 4 days by Alzet pump, did not increase salt appetite though the infusion was calculated to produce moderate reduction of CSF [Na]. It would appear that there may be significant species differences in effect of reduced CSF [Na] on salt appetite.

Animals↗
PubMed1984

What makes wild rabbits drink?

Wild rabbits Oryctolagus cuniculus (L) introduced to Australia over a century ago successfully colonized diverse environments in a large part of the continent varying from arid desert, alps, to lush grasslands and coastline where water and salt may be either abundant or very scarce. Wild rabbits caught in Northern Victoria were studied under laboratory conditions, where they adapted to dry pelleted food and drank regularly water and a cafeteria of electrolyte solutions offered. Intracerebroventricular (IVT) infusion of angiotensin II (AII) in doses 10, 50 and 500 ng/h did not increase their water drinking, but increased salt appetite, although it was delayed one or more days after the beginning of AII infusion. IVT infusion of AII 500 ng/h for one day caused a halving in water intake and a tenfold increase in sodium excretion. These were followed by compensatory changes in water and 0.5 M NaCl intake on the consecutive days. IVT infusion of AII 50 ng/h for one day induced an increased urinary sodium excretion, a negative sodium balance which was not followed by an increased salt appetite. IVT infusion of AII 10 ng/h for five days caused a progressive increase in sodium excretion and salt appetite which were significant on the fourth day of infusion and both remained eight-ten times greater than control levels for three days after the cessation of infusion. Water intake was unchanged. IVT infusion of 0.3 M Na-CSF for two days reduced water and food intake, and caused a negative sodium balance on the second day of infusion which was not followed by increase in salt appetite.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1984

Dietary modulation of estrous cyclicity in singly and multiply housed C57BL/6J mice.

Two commercial diets differed markedly in their ability to support estrous cyclicity in both singly and multiply housed, 3- to 4-month-old virgin C57BL/6J mice. When fed a breeder diet developed to promote reproduction, mice had shorter cycles and a decreased number of acyclic intervals than when fed a standard diet. In addition, the breeder diet counteracted the inhibitory influence of multiple housing on cyclicity. Although the breeder diet had a three-fold higher fat content and a two-fold lower fiber content, it was not possible to ascribe a causal role to these differences since the diets differed in the relative amounts and sources of many other components.

Animal Feed↗
PubMed1983

Water drinking and the effect of angiotensin and renin in a dasyurid marsupial (Antechinus stuartii).

Marsupial mice, Antechinus stuartii, were given intraperitoneal (ip) injections of 1-30 micrograms of Val5-angiotensin II amide to determine whether it had any effect on thirst. Drinking in the first hour after injection and measured water intake over 2 and 24 hr were not substantially increased compared with controls. Intraperitoneal injection of sheep renin had no effect on water intake. Water deprivation increased 2- and 24-hr water intake. Sheep renin and Val5-angiotensin II amide elicited pressor responses after ip injection. By comparison, rats given 100 micrograms of Val5-angiotensin II amide ip increased water intake in the first 2 hr after injection compared with saline-injected and noninjected controls. The results suggest that the thirst mechanism in Antechinus is insensitive to exogenous and to low levels of endogenous circulating angiotensin II. The explanation of this difference from other mammals may be found in evidence that the thirst mechanism in species which do not normally drink water in nature is relatively insensitive to exogenous angiotensin.

Angiotensin II↗
PubMed1983

Revascularization and healing of onlay particulate allogeneic bone grafts in primates.

Particle size of allogeneic bone grafts was investigated to determine its effect on revascularization and healing. Freeze-dried chips of different sizes were placed on the monkey lateral mandibular cortex, and the subsequent healing and revascularization were studied by histologic, autoradiographic, and microangiographic techniques. It appears that allogeneic bone is a reasonable substitute for autologous bone in mandibular ridge augmentation procedures.

Animals↗
PubMed1983

Restoration of ovulatory cycles by young ovarian grafts in aging mice: potentiation by long-term ovariectomy decreases with age.

The relative contributions of ovarian and hypothalamic-pituitary factors to the anovulatory status of aging mice were evaluated by measuring the capacity of mice to resume ovulatory cyclicity after receiving young ovaries under the renal capsule. Young grafts partially restored cyclicity if old hosts were acutely ovariectomized but almost fully restored cyclic ovulatory function if the old hosts had been ovariectomized early in adulthood. With advancing age, however, the efficacy of the grafts declined progressively in both acute and long-term ovariectomized groups. These data show that both ovarian and hypothalamic-pituitary aging contribute to the etiology of anovulation. Although chronic withdrawal from ovarian secretions retards the age of onset of hypothalamic-pituitary aging, the duration of this ameliorative effect is limited by progressive ovary-independent neuroendocrine dysfunction.

Aging↗
PubMed1983

Imminent oocyte exhaustion and reduced follicular recruitment mark the transition to acyclicity in aging C57BL/6J mice.

Quantitative cytological analyses of aging C57BL/6J mouse ovaries revealed that the populations of primordial and growing follicles were nearly exhausted by 13-14 months, the average age of ovulatory failure. Anovulatory animals of this age had, on the average, half the follicle number of their counterparts which were still ovulating. This result suggests that follicular depletion is a factor which contributes to the loss of ovarian cyclicity during aging. However, the considerable overlap of follicle number between the two groups suggests that other, possibly extraovarian, factors also influence the loss of ovulatory function. Although the numbers of follicles recruited for growth was much lower in ovaries from old cycling animals, the number of ova shed cyclically was generally within the range of younger individuals. The observed reduction in incidence of morphological atresia among medium-sized follicles may explain how ovulatory constancy is maintained virtually throughout the cyclical life of the ovary.

Aging↗
PubMed1983

Dehydration induces sodium depletion in rats, rabbits, and sheep.

The effect of water deprivation for 1 day on Na balance was measured in rats, rabbits, and sheep. In all three species, dehydration induced a considerable increase in the daily output of Na in urine. This resulted in the water-deprived animals becoming Na depleted as well as water deficient. Experiments were also designed to control for the reduced food intake that results from water deprivation in rats and rabbits. The results showed that decreased food intake was not the cause of the natriuresis and subsequent Na depletion that occurred during dehydration. When water was again made available to the dehydrated animals, a period of urinary Na retention ensued. This Na retention usually continued until the Na deficit that had accrued during the period of dehydration had been ameliorated. It seems likely that natriuresis in response to dehydration is common in mammals. We postulate that such a natriuretic response may serve a homeostatic function in buffering increases in plasma [Na] and osmolality that result from dehydration.

Animals↗
PubMed1983

A comparison of rectangular and cylindrical collimation for intraoral radiographs.

This study was conducted to compare the type and frequency of cone-cuts that occur with rectangular and cylindrical collimation in dental radiography. Thirty-eight hundred radiographs, half made with cylindrical cones and half made with rectangular cones, were examined for major and minor cone-cuts. A total of 156 cone-cuts was found. Thirty-three of these were of the major category, 86 percent of which occurred with rectangular collimation. Although cone-cuts appeared much more frequently when a rectangular cone was used, a significant reduction in useless radiation makes this type of collimation a worthwhile consideration.

Equipment Design↗
PubMed1982

A longitudinal study of estrous cyclicity in aging C57BL/6J mice: I. Cycle frequency, length and vaginal cytology.

Cycle frequency, length, and vaginal cytology were measured longitudinally in three cohorts of singly housed virgin mice staggered across a 3-year interval. The age profiles of these parameters were qualitatively similar, but quantitatively different, among cohorts. Cycle frequency was initially low (Phase I), due to prolonged cycles and late-starting cycles, and did not peak (Phase II) until mice were 3-5 months old. Phase II lasted for 7-10 months, depending on the cohort. Thereafter cycle frequency declined steadily (Phase III). The average age of cessation of cyclicity varied among cohorts, occurring between 13 and 16 months of age. Age changes in cycle length paralleled those of cycle frequency. During Phase II, median cycle length was less than 5 days and variance was lowest. During Phases I and III, variance was about twofold greater and median cycle length was greater than 5 days. Although median cycle length remained stable for several months during Phase II, the peak period of 4-day cycles was much shorter. In all cohorts, 4-day cycles did not peak until 7-8 months of age and began to decline by 9 months. The decrease in 4-day cycles was associated with a progressive lengthening of cycles-first from 4 to 5 days, then to longer cycles. The fraction of cycles with extended cornification (greater than 2 days) increased with advancing age from less than 0.35 during the initial period of cycle lengthening to a maximum of 0.60. The observation that the initial phase o cycle prolongation was not usually associated with extended cornification is consistent with earlier evidence that this period is characterized by a delayed, rather than prolonged, preovulatory rise of estradiol. However, the increased fraction of prolonged cycles with extended cornification at later ages suggests that the preovulatory elevation of estradiol may ultimately be prolonged.

Aging↗