Effect of age on cardiovascular responses to static muscular contraction in beagles.

Induced muscular contraction in anesthetized animals results in significant hemodynamic and regional blood flow (RBF) changes. Although reflex cardiovascular responses initiated in contracting muscle have been firmly established, little is known about the effects of age on these responses. Because other reflex responses that involve sympathetic activation appear to be attenuated with age, it was hypothesized that reflex efferent cardiovascular responses that normally occur during muscular contraction would be impaired in senescent dogs. Therefore, hemodynamic and RBF responses to induced static hindlimb contraction (HLC) were evaluated in 8- to 14- and 2- to 3-yr-old beagles during alpha-chloralose anesthesia. Most baseline hemodynamic parameters were similar in both groups, but heart rate was significantly (P < 0.05) higher in old dogs. During HLC, heart rate and blood pressure increased in the young and old dogs. However, increases in stroke volume and cardiac output were greater in old dogs, combined with a reduction in systemic vascular resistance not observed in young dogs. No age-related difference in baseline RBF (microspheres) was observed in six of eight abdominal regional circulations and in each of four skeletal muscle groups. During HLC, RBF reductions occurred in six of eight abdominal organs in young and old dogs. However, the reduction in RBF and concomitant increase in vascular resistance in all eight abdominal regions combined was almost twice as great in young vs. old dogs. In noncontracting skeletal muscle, RBF decreased and vascular resistance increased four times more in young vs. old dogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hematologic and serum chemistry studies in rats exposed to 60-Hz electric fields

Numerous hematologic and serum chemistry variables were examined in rats exposed to unperturbed 60-Hz electric fields at 100 kV/m for 15, 30, 60, or 120 days. Each study was replicated once. Rigorous statistical evaluations of these data did not detect any consistent effect of the electric field for exposures of up to 120 days. It was, however, not unusual in any individual study to detect certain variables that were significantly different between the exposed and sham-exposed animals. This emphasizes the need for replicate designs and appropriate statistical analyses when investigating chemical or physical insults that may have minimal influence on biologic function.     

Structural changes in the granulosa lutein cells of pregnant cows between 60 and 245 days.

The structural changes in the granulosa lutein cells in the pregnant cows between 60 and 245 days, were observed. The polyhedral or pump cells has an acidophilic cytoplasm around the spherical nucleus. The glycogen granules increased in number up to 230 days of pregnancy. The lipid globules increased in size and amount during advanced pregnancy. The mitochondria showed a wide range of variations in shape and size. The matrix of many mitochondria contained dense inclusions which replaced the entire matrix in late pregnancy. The endoplasmic reticulum was chiefly of smooth type but a few stacks of the rough variety could be seen in the early days of pregnancy. Sometimes, whorls of smooth-surfaced endoplasmic reticulum enclosing mitochondria were seen. The Golgi complex was fully developed in the granulosa cells of all cases studied. The dense granules and lipid globules increased in size and number in the older corpora lutea. The cell surface showed numerous infolding of the plasma membrane.     

Serum chemistry values of normal dogs (beagles): associations with age, sex, and family line

One hundred and sixteen colony control dogs (purebred beagles) ranging in age from 56 to 4868 days at the time of sampling, were tested at various intervals over a 10-year period to determine the normal values of several serum constituents. The effects of sex and family line were also noted. With increasing age, serum glutamic-pyruvic transaminase, total protein, and cholesterol increased, whereas glucose, serum glutamic-oxalacetic transaminase, creatine phosphokinase, iron, alkaline phosphatase, and albumin decreased. Females had significantly higher levles of urea nitrogen, iron, and cholesterol than males. Males had significantly higher serum glutamic-pyruvic transaminase levels. The rate of increase in serum cholesterol with age was greater in males than in females. Males showed no age related changes in levels of urea nitrogen or iron, while the females showed decreasing levels. Significant differences in total protein and albumin were noted in dogs belonging to different family.     

The effect of perinatal 60Co gamma radiation on brain weight in beagles

Beagle dogs were given single, whole-body 60Co gamma-radiation exposures at one of three prenatal (8, 28, or 55 days postcoitus) or three postnatal (2, 70, or 365 days postpartum) ages to evaluate the relative radiosensitivity of various stages of brain development. A total of 387 dogs received mean doses ranging from 0.16 to 3.83 Gy, and 120 dogs were sham-irradiated. Groups of dogs were sacrificed at preselected times from 70 days to 11 years of age. Brain weight decreased significantly with increasing dose in dogs irradiated at 28 or 55 days postcoitus or at 2 days postpartum. Irradiations at 28 days postcoitus were dramatically more effective in causing a reduction in brain weight than those at 55 days postcoitus or 2 days postpartum. Among dogs given 1.0 Gy or more and followed for up to 4 years, there was a radiation effect evident at all three sensitive exposure ages. Among dogs given lower doses and followed for up to 11 years, there was a significant decrease in brain weight in dogs given 0.80-0.88 Gy at 28 days postcoitus. All decreases in brain weight were present after normalization for radiation-induced reductions in skeletal (body) size. No specific morphologic changes were noted in the brains which showed the radiation-related reductions in size.     

Ultrasonographic evaluation of the conceptus from days 10 to 60 of pregnancy in jennies

Daily ultrasound examinations were conducted from Days 10 to 60 (ovulation = Day 0) of pregnancy to monitor the conceptus in jennies (n = 12). The embryonic vesicle was first detected on Day 11.5 +/- 0.9 (mean +/- SD; range 10 to 13 d) and was mobile until movement ceased (fixation) on Day 15.5 +/- 1.4 (range, 13 to 18 d). The vesicle was spherical from Days 10 to 18 (mean growth rate, 3.2 mm/d), non spherical (irregular) with a reduced growth rate (0.5 mm/d) from Days 19 to 29, and then grew at a moderate rate (1.6 mm/d) up to Day 46. On average, detection of the embryo proper (consistently located on the ventral aspect of the yolk sac) and embryonic heartbeat were Days 20.7 +/- 1.2 and 23.5 +/- 1.3, respectively. Formation of the allantoic sac was first detected on Day 24.4 +/- 1.7 and was complete on Day 36.8 +/- 1.6. Descent of the fetus (and formation of the umbilical cord) began on Day 37.9 +/- 1.7 and was complete on Day 44.1 +/- 2.1. Crown-rump length averaged 3.7, 15.4, 22.7, 37.5 and 59.6 mm on Days 20, 30, 40, 50 and 60, respectively. In general, morphologic features and dates of occurrence were similar to those reported previously in the mare.     

Mitochondrial changes in flight muscles of normal and flightless Drosophila melanogaster with age

Fine structural changes in mitochondrial morphology pertaining to size, number and growth were examined in flight muscles of normal and experimentally dewinged male Drosphila melanogaster ranging up to 26 days of age. In the normal winged flies, the number of mitochondria decreases during the first week of adult life whereas the size of individual mitochondrial profile increases significantly. Changes in mitochondrial size and number are due to the fusion of mitochondria. Fused mitochondria are extremely large in size and irregular in shape. In 26-day old normal flies, the number of mitochondria increases while the mitochondrial size is reduced indicating mitochondrial division. In comparison to the normal flies, dewinged flies exhibit a similar degree of mitochondrial fusion and growth during the first week of life. However, the extent of mitochondrial fission in 26-day old dewinged flies is greater than in the normal flies of this age. Structural mechanisms of mitochondrial fusion and fission are described. The objective of this study was to examine the relative effects of age and flight activity on the mitochondria.     

Successive changes in the blood composition of experimental normal beagle dogs associated with age

Eight hematologic parameter values, 16 serum biochemical constituents, serum protein fractions and albumin-globulin ratios were determined in blood samples obtained from 879 normal, healthy Beagle dogs of both sexes which had been reproduced and bred in our laboratories. The blood samples were collected from the Beagles that ranged in monthly ages from 1 to 12 and in monthly ages from 13 to 121, which were classified as the adult class. As a result, red blood cell counts, hemoglobin concentrations and packed cell volumes increased with growth. Red blood cell parameters of normal Beagles in our laboratories were rather higher than those in literatures presented by many other researchers. MCV decreased and MCHC increased gradually with age. Total serum protein concentrations increased with growth. alpha 1-1 and alpha 1-2 Globulin fractions descended, but beta 2 and gamma globulin fractions ascended in serum proteins. Alkaline phosphatase activities, inorganic phosphorus concentrations and glucose concentrations decreased conspicuously with growth. Leucine aminopeptidase activities and calcium concentrations decreased slightly. Serum cholinesterase and LDH activities showed a tendency to diminish similarly. Blood urea nitrogen and creatinine concentrations multiplied gradually. Hematologic parameters became almost steady in our 7-month-old dogs or older ones and serum biochemical constituents had a tendency to be stable in our 7- to 9-month-old dogs or older ones in the blood. White blood cell counts, alkaline phosphatase activities, inorganic phosphorus concentrations, glucose concentrations, leucine aminopeptidase activities and calcium concentrations were lowest in the adult class.     

Two abnormalities of hexosaminidase A in clinically normal individuals

Two abnormalities of beta-hexosaminidase A (HEX A) activity are described. One, found in two unrelated Jewish children, was characterized by the complete absence of HEX A activity in serum, but low levels of activity in leukocytes and fibroblasts using artificial substrate. The other, found in a non-Jewish man, was characterized by uniformly low levels of HEX A activity in leukocytes, fibroblasts, and serum against artificial substrate. In all cases, the pH optimum of HEX A was normal, there was no increased lability at 37 degrees C, and no inhibitor was detected to account for the deficiency of activity. Cultured fibroblasts of these individuals were capable of synthesizing and processing alpha- and beta-subunits of HEX A and capable of cleaving GM2 ganglioside. The patients, ranging in age from 6 to 30 years, are clinically normal. They are probably genetic compounds carrying the classical Tay-Sachs gene and a differently mutated allele that imparts the anomalous phenotypic features observed.