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Biomedical subjects

M A Walker

Publications and source records attributed to M A Walker.

At least 73 records · Page 4Linked to original sources
PubMed1988

Effects of age and of early lighting on ovarian function in breeding turkeys.

1. Yellow follicle numbers and production of defective egg shells were greater in the early part of the laying period in conventionally-reared turkeys photostimulated at 24 rather than 30 weeks of age. 2. The number of yellow follicles declined with age and were similar in both groups at 40 weeks of age. 3. At 55 weeks of age more birds photostimulated at 24 weeks were out of lay and birds in lay had fewer yellow follicles and more atresia compared with turkeys photostimulated at 30 weeks of age. 4. The numbers of white follicles in the 1 to less than 2 mm size were similar in the two groups at each age. The proportion of white follicles which were atretic was negatively related to the number of yellow follicles, particularly in follicles 5 to less than 8 mm diameter.

Age Factors↗
PubMed1988

Radiographic findings in a canine model of mucopolysaccharidosis I. Changes associated with bone marrow transplantation.

Eight dogs with mucopolysaccharidosis I (MPS I) were studied and their radiographic lesions compared with those reported in human MPS I. Three of the dogs received bone marrow transplants from unaffected littermates at 5 months of age. These dogs, and two affected control littermates were radiographed at 3, 6, 9, 12, 15, 18 and 20 months post-transplantation to evaluate the effects in chondro-osseous tissues. Although bone marrow transplantation did not alleviate all radiographically detectable changes, there was delayed onset of some lesions and reduced severity of most lesions in the dogs receiving transplants. Those lesions most closely associated with clinical lameness or gait abnormalities in untreated canine MPS I were most improved (or eliminated), and this was reflected in marked clinical improvement.

Animals↗
PubMed1988

Histological study of follicular atresia in the ovary of the domestic hen (Gallus domesticus).

Semi-serial (1 in 20) sections of ovaries were studied and only two types of atresia were identified--non-bursting and bursting. Smaller, non-yolky follicles (less than 1 mm diameter) showed non-bursting atresia. Atresia in follicles greater than 1 mm diameter was invariably of the bursting type which involved the rupture of the follicular wall, and the extrusion of yolk and cellular debris through the rupture site into the stroma. However, this rupture site was small and consequently was not visible in every section but it could always be seen when the follicle was followed in semi-serial sections. The mitotic index of granulosa cells in bursting atretic follicles was much lower than that for normal follicles. The most common criteria for distinguishing non-bursting atretic follicles were the extremely shrunken, irregularly shaped oocytes and the separation of the granulosa from the theca. In bursting atretic follicles, reliable indications were the presence in the ooplasm of some cells or cellular debris, and disorganization of the yolk and granulosa tissue. The presence of pycnotic nuclei in the granulosa cells was not a consistent feature of all atretic follicles of the hen.

Animals↗
PubMed1988

Distribution of follicular growth, atresia and ovulation in the ovary of the domestic hen (Gallus domesticus) at different ages.

Ovaries of laying hens of 14, 18, 30, 45 and 86 weeks of age were divided transversely into two or more distinct regions. Differences in follicular populations between these regions were observed. The central segments of the ovary in birds of 14 weeks of age produced most of the visible (greater than 0.5 mg) developing follicles (P less than 0.01). This was a transient effect during ovarian maturation. In birds of 18 weeks of age, but not yet in lay, more follicles of greater than 8 mm in diameter were observed in the anterior part of the ovary than the posterior part (P less than 0.05). Follicles of this size are almost certain to ovulate. The posterior segment of the ovary of birds of 30, 45 and 86 weeks of age contained more follicles beginning the rapid growth phase, as measured by follicles of 1.4-1.8 mm in diameter, than did the anterior segment (P less than 0.01). Higher levels of atresia in the posterior segment (P less than 0.001) resulted in fewer follicles of greater than 8 mm (P less than 0.001) and fewer post-ovulatory follicles than in the anterior segment. We conclude that most of the eggs produced during the hen's laying year must be from ovulations from the anterior part of the ovary.

Aging↗
PubMed1987

Radiotherapy of malignant nasal tumors in 67 dogs.

The nasal cavity of 67 dogs with malignant nasal neoplasia was treated with radiation. Preirradiation surgical cytoreduction of the tumor was done in 41 dogs. Fifty dogs were irradiated by use of 10 fractions over 22 days, and 17 dogs were given a similar total dose in 5 fractions over 35 days. The range of survival times (0.5 to 42 months), median survival time (8.5 months), and 1- and 2-year survival rates (38% and 30%, respectively) were better than those expected for other methods of treatment. Serious complications were few (4%). Survival times for dogs were determined on the basis of histologic tumor type and on the basis of megavoltage (cobalt or linear accelerator) vs softer deep radiation (cesium or orthovoltage) treatment, with or without cytoreductive surgery. Survival times of 10 dogs given softer radiation without surgery were shorter than those of 14 dogs that were given softer radiation and had cytoreductive surgery. Survival times of dogs that were given softer radiation and had surgery were similar to those of dogs that were given megavoltage radiation only. Cytoreductive surgery did not improve survival times for dogs that were given megavoltage radiation. Median survival time for 38 dogs with adenocarcinoma was 12 months, compared with 6 months for 14 dogs with squamous cell or undifferentiated carcinoma. Median survival time for 16 dogs with a variety of sarcomas was 11.2 months. Survival times of dogs with adenocarcinoma or sarcoma were significantly better (P less than 0.02 or 0.03) than for dogs with squamous cell or undifferentiated carcinoma. Necropsies were performed on 27 of 58 dogs that died or were euthanatized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1987

Occurrence of waxy-textured yolk in the egg of the domestic hen (Gallus domesticus).

An unusual yolk material (waxy yolk) was identified in some hard boiled yolks of one strain of domestic hen. Its structure was consistent with it being formed from normal yolk through disruption of the yolk spheres. These are normally stable during even long periods of storage. Formation occurs mainly after ovulation, during passage of the egg down the oviduct; only rarely could it be found in the larger follicles of the ovarian hierarchy. In the flock of birds examined the incidence of eggs with waxy yolk was 75% of all eggs laid over a 7 d period. Of the 173 birds tested, the eggs of only 17 birds were totally unaffected; all eggs of 82 birds contained this material. The results of a hatchability trial indicated this material had no apparent influence on the embryo or hatchability.

Animals↗
PubMed1987

Observations on the size of the follicular hierarchy in the turkey hen and a case of arrested follicular growth.

1. The phase of rapid development of ovarian follicles in turkeys fed ad libitum or given a restricted allocation of food from 6 to 30 weeks of age was determined by feeding a fat soluble dye and counting the number of rings of dye in the yolks of laid eggs. 2. The duration of rapid growth was similar in ad libitum and restricted birds and averaged 11.6 d. The maximum number of yellow follicles greater than 8 mm expected in the hierarchy of the turkey hen is 9 to 10 compared with 6 to 7 in the chicken. 3. Discontinuous growth was observed in a series of follicles from one bird. This is believed to be the first report of arrested follicular growth in the turkey.

Animals↗
PubMed1987

Effect of a freeze-thaw cycle on properties of microsomal membranes from wheat.

A freeze-thaw cycle to -12 degrees C induced several physical and compositional changes in the microsomal membranes isolated from crown tissue of winter wheat (Triticum aestivum L. cv Frederick). Exposing 7-day-old, nonacclimated seedlings to a single freeze-thaw cycle prevented regrowth of the crown and resulted in increased membrane semipermeability. The phospholipid and protein content of microsomal membranes isolated from the crowns decreased by 70 and 50%, respectively. Microsomal membranes isolated after the lethal freeze-thaw stress, and liposomes prepared from total membrane lipids, exhibited greater microviscosity, measured by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. The number of free thiol groups per milligram membrane protein, measured using the specific fluorescent probe, N-dansylaziridine, decreased after freezing. In contrast, acclimated wheat seedlings which showed increased freezing tolerance, as indicated by survival and ion leakage, suffered almost no effects from the freeze thaw treatment as determined by measurements of membrane microviscosity, phospholipid content, protein content, or danzylaziridine fluorescence. An examination of membranes isolated from frozen tissue showed that most of the changes occurred during the freezing and not during the thawing phase.

Journal Article↗
PubMed1987

Subcellular Localization of Amines and Activities of Their Biosynthetic Enzymes in p-Fluorophenylalanine Resistant and Wild-Type Tobacco Cell Cultures.

Three levels of free amines and the activities of their biosynthetic enzymes were measured in subcellular fractions of two cell lines of Nicotiana tabacum L. cv Xanthi. The TX4 cell line, a p-fluorophenylalanine resistant culture which accumulates high levels of cinnamoylamides, was compared to the wild-type culture TX1. In cells harvested on day 6 of the growth cycle, nearly all free putrescine, spermidine, and tyramine was found in the supernatant fraction of both cell lines. Although a consistent portion of ornithine decarboxylase activity was detected in the nuclear-enriched fractions of TX1 and TX4, the largest levels of activity were in the supernatants of both lines. In TX1, arginine decarboxylase activity was low relative to that of ornithine decarboxylase, but, in the TX4 line arginine decarboxylase levels in the cytosol were substantially elevated. Tyrosine decarboxylase was not detected in 6-day-old TX1 cells, but significant amounts of activity were measured in the 1000g and supernatant fractions of TX4. S-Adenosylmethionine decarboxylase activity was low in both cell lines and was located predominantly in the supernatant.

Journal Article↗
PubMed1987

Inhibition of fibrosis in TSK mice by blocking mast cell degranulation.

The Tsk mouse has a genetically transmitted connective tissue disease whose skin lesions resemble those of scleroderma. After treatment with disodium cromoglycate, a marked decrease in skin fibrosis was observed, raising the possibility that disodium cromoglycate may be a potential treatment for human scleroderma.

Animals↗
PubMed1986

Prevention of postmetrizamide myelographic seizures in dogs, using 5% dextrose solution.

Diuresis by IV administration of 5% dextrose in a balanced electrolyte solution (BES) reduced the frequency of occurrence of postmyelographic seizures in dogs. In the first study, a single myelogram was obtained in 8 dogs without dextrose diuresis. Two of these dogs weighed greater than 15 kg and both had seizures after metrizamide myelography. The remaining 6 dogs weighed less than 15 kg and only 2 had seizures. Greater body weight may have increased the risk of postmyelographic convulsions. In a crossover study, myelograms were obtained in 12 dogs weighing 20 to 31 kg. Six dogs were given 5% dextrose in BES (20 ml/kg of body weight/hr [diuresed]) and 6 were given BES alone (10 ml/kg/hr [not diuresed]). When myelography was repeated 10 days later, the 6 dogs that had been given 5% dextrose in BES were given BES only and the 6 dogs that had been given BES alone were given 5% dextrose in BES. The frequency of convulsions after metrizamide myelography was lower when dogs were given dextrose (33%) than when they were not (100%).

Animals↗
PubMed1986

Radial nerve cross-finger flap differential nerve contribution in thumb reconstruction.

Six patients with extensive palmar thumb pulp and soft tissue loss were treated with a staged transfer of radial nerve innervated flap tissues from the dorsum of the index finger. They were followed for a mean period of 3 years. This transfer of radial nerve innervated dorsal index finger tissues to the palmar surface of the thumb has been a successful method of innervation restoration. The ultimate sensibility of the reconstructed thumb seems to be a mixture of median and radial nerve sensibility. Sensory testing shows that after transfer, the ulnar side of the flap is more innervated from the radial nerve than the radial side. Our findings suggest that the presence of active sensory axons in the radial nerve innervated flap may play an inhibitory role in direct and/or functional neurotization of the transferred flap.

Adult↗
PubMed1986

Changes in Amines and Biosynthetic Enzyme Activities in p-Fluorophenylalanine Resistant and Wild Type Tobacco Cell Cultures.

The levels of free amines and the activities of their biosynthetic enzymes were measured in a p-fluorophenylalanine resistant Nicotiana tabacum L. cv Xanthi cell line (TX4) which accumulates high levels of cinnamoylamides, and a wild type cell line (TX1). Putrescine in TX1 and spermidine in TX1 and TX4 increased 4-fold by day 4 but declined by day 8 of the culture period. Spermine levels were consistently low, while tyramine was not found in TX1 until day 9 when a gradual rise was noted. Ornithine decarboxylase activity in TX1 and TX4 increased slightly through day 2 but declined gradually thereafter. S-Adenosylmethionine decarboxylase activity remained low throughout the culture period, and tyrosine and arginine decarboxylases in TX1 were very low in activity. In contrast, the activities of tyrosine and arginine decarboxylases were elevated in TX4, but a 3-fold increase in tyramine after a subculture was not accompanied by a rise in tyrosine decarboxylase. However, tyrosine decarboxylase activity did increase during a second rise in tyramine levels in aging cells, late in the culture period. Although significant differences exist in amine levels, between TX4 and TX1, it is unclear how altered amine metabolism relates to p-fluorophenylalanine resistance.

Journal Article↗
PubMed1985

Heart failure caused by gossypol poisoning in two dogs.

Two hound-type dogs from the same kennel were admitted in terminal stages of congestive heart failure. An investigation revealed the owner had been feeding the dogs cottonseed meal daily with their kibbled meal. Gossypol toxicosis from feeding this meal caused marked abnormalities in myocardial contractility. Although in severe congestive heart failure, one dog had only minimal dilatation of its heart, as revealed by thoracic radiography. Disseminated intravascular coagulopathy also was diagnosed in this dog. Gossypol is a cumulative toxin; the amount of free gossypol fed was approximately 5.4 to 5.7 mg/kg/day for an unknown duration.

Animals↗
PubMed1985

Comparison of the response in vivo to luteinizing hormone and follicle stimulating hormone of the granulosa of six follicles from the ovarian hierarchy in the chicken (Gallus domesticus).

A function test was used to compare the response of the granulosa from the six largest preovulatory follicles. F1-F6, of laying hens to ovine LH (40 micrograms), ovine FSH (1200 micrograms), and PMSG (800 micrograms). The progesterone content of these granulosa which were dissected out exactly 45 min after the injection, was measured by radioimmunoassay. With each of the three gonadotropin preparations, the amount of progesterone accumulating in the F1-F3 granulosa always exceeded that of F4 and F5. The values were two to six times greater than those obtained in tissue from control hens injected with 1% bovine serum albumin (BSA). The levels in the smallest F6 granulosa did not differ from those of BSA-treated controls. LH had the greatest stimulatory effect on the granulosa response. The results indicate that the production of progesterone by the granulosa of the F1-F5 follicles in vivo may be controlled mainly by LH, rather than FSH. The observed changes induced by the FSH and PMSG preparations could be attributed to their LH content. The granulosa of the F1 and F2 follicles are the major contributors to the circulating progesterone in the blood plasma of the laying hen.

Animals↗