Biomedical subjects

L A Willingham

Publications and source records attributed to L A Willingham.

6 recordsLinked to original sources

PubMed2001

Potential for cloning dogs.

The aim of this study was to determine whether nuclear transplantation could be used to clone a dog using donor nucleus cells collected from an adult female. Fibroblasts obtained from skin biopsies were fused with enucleated bovine or canine oocytes. The resulting cloned embryos were cultured in vitro to monitor embryonic development. A proportion of the resulting embryos was transferred into surrogate bitches for development to term. When canine oocytes were used as recipient ova for canine fibroblasts, 23% of the resulting embryos cleaved at least once after culture in vitro. Five cloned embryos were transferred into three synchronized recipient bitches, but no pregnancies resulted. When bovine oocytes were used as recipinets for canine fibroblasts, 38% cleaved to the two- to four-cell stage and 43% cleaved to the eight- to 16-cell stage. Forty-seven of these embryos were transferred into four recipient females, resulting in a single conceptus that ceased development at about day 20 of gestation. The desire for cloned dogs is considerable and will undoubtedly incite the development of successful methods for cloning companion animals. However, significant investment into additional research is required, especially in the areas of in vitro maturation of oocytes and control of the oestrous cycle of bitches.

Animals↗

PubMed1999

A novel lipoprotein from the hemolymph of the cochineal insect, Dactylopius confusus.

A new type of insect lipoprotein was isolated from the hemolymph of the female cochineal insect Dactylopius confusus. The lipoprotein from the cochineal insect hemolymph was found to have a relative molecular mass of 450 000. It contains 48% lipid, mostly diacylglycerol, phospholipids and hydrocarbons. The protein moiety of the lipoprotein consists of two apoproteins of approximately 25 and 22 kDa, both of which are glycosylated. Both apolipoproteins are also found free in the hemolymph, unassociated with any lipid. Purified cochineal apolipoproteins can combine with Manduca sexta lipophorin, if injected together with adipokinetic hormone into M. sexta. This could indicate that the cochineal lipoprotein can function as a lipid shuttle similar to lipophorins of other insects, and that the cochineal insect apolipoproteins have an overall structure similar to insect apolipophorin-III.

Amino Acid Sequence↗

PubMed1996

Variations in the density of lipophorins during late larval and early pupal development of Manduca sexta.

The density of lipophorin was determined in individual Manduca sexta during development from the second day of the fifth larval instar to the second day of the pupal stage. Lipophorin formed defined bands when subjected to density gradient ultracentrifugation. All lipophorin observed was high density lipophorin; however, the densities varied from 1.100 to 1.184 g/ml, and 40% of the animals had more than one density form of lipophorin. The lipophorins were divided into five density classes: class 1 from 1.100 to 1.113 g/ml, class 2 from 1.114 to 1.132 g/ml, class 3 from 1.133 to 1.145 g/ml, class 4 from 1.146 to 1.162 g/ml, and class 5 from 1.163 to 1.184 g/ml. In feeding larvae, classes 2 and 3 were the most abundant. Larvae of the first day of wandering had either lipophorin in class 2 or in classes 2 and 5. Later during wandering the variation increased, but on the third day most of the lipophorin was in class 2. In first day pupae, only lipophorins of classes 4 and 5 were detected, while on the second day of the pupal stage, classes 2 and 3 were predominant. Class 1 lipophorin was abundant in larvae injected with Manduca adipokinetic hormone (M-AKH), and rare in young feeding larvae. In no other stage was class 1 lipophorin observed. Our results show that the density of lipophorin is much more variable than previously reported which makes it difficult to ascribe any lipophorin density to a developmental stage. These results also show that adipokinetic hormone decreases the density of lipophorin in larvae.

Animals↗

PubMed1995

Apolipophorin-III and adipokinetic hormone in lipid metabolism of larval Manduca sexta.

The hemolymph lipid levels were measured and the density of lipophorin was determined during late larval development in Manduca sexta. During the feeding phase of the 4th and 5th instar larvae the lipid level in hemolymph remained largely unchanged at less than 2 mg/ml. During the molt from 4th to 5th instar, the hemolymph lipid level increased, but decreased after feeding restarted in the 5th instar. In wandering larvae and prepupae the hemolymph lipid level increased from about 2 to nearly 10 mg/ml. The density of lipophorin from feeding larvae was found to be 1.148 g/ml with minor amounts of lipophorin having a lower density of about 1.128 g/ml and sometimes a small amount with a density of 1.174 g/ml. In molting larvae, however, the density was clearly lower, 1.116 g/ml. In wandering larvae of all ages, two predominant forms of lipophorin were observed; the density of these forms was 1.132 g/ml and 1.177 g/ml. Rarely, one or three different forms of lipophorin were observed. While the lipophorin of feeding larvae contains only apoLp-I and II (and lipids), the lipophorin of molting larvae contains in addition apoLp-III. ApoLp-III is seldom present in lipophorin from wandering larvae. According to our current models, lipophorin can take up only a certain amount of diacylglycerol before it needs apoLp-III for surface stabilization. Injection of 1 pmol of M. sexta AKH into feeding larvae increased the hemolymph lipid level, decreased the density of lipophorin to 1.125 g/ml and resulted in the association of apoLp-III with lipophorin. Cardiacectomy did not prevent feeding larvae from developing to wandering larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Migrated fetal astrocytes modulate nerve growth factor expression in host nucleus gracilis of the medulla after grafting in third cervical hindlimb dorsal columns of the spinal cord.

Nerve growth factor (NGF) immunoreactivity in the nucleus gracilis of the medulla was quantitated for 90 days after aspiration of the C3 spinal hindlimb dorsal columns of 36 adult rats. Half the lesioned animals were a lesion-only group. The remaining lesioned animals received an immediate graft of two 1.0-mm pieces of 14 day gestation fetal rat cervical spinal cord (prelabeled with Phaseolus vulgaris leucoagglutinin) into the aspiration pocket (graft group). There were 3 normal controls. Groups of animals were analyzed at 7, 14, 21, 30, 60, and 90 days. At 90 days, NGF immunoreactivity was significantly elevated in the nucleus gracilis of lesion-only animals. This increase in NGF immunoreactivity was augmented in glial end-feet surrounding neurons and was also observed in the cytoplasm of astrocytes and some neurons. Previous experiments have shown that the cluster neurons of the nucleus gracilis undergo atrophy at this time with a concomitant decrease in hindlimb placement. NGF immunoreactivity (90 days) in grafted animals, however, was significantly less than in lesion-only animals (P < 0.05) but remained significantly elevated above control animals (P < 0.05). Unlike in lesion-only animals, there were no NGF positive neurons in the nucleus gracilis of grafted animals. Previous experiments have shown that astrocytes from fetal spinal cord grafts migrate to the nucleus gracilis, maintain cluster neuron cell size, and improve hindlimb placement at 90 days. The present data indicate that modulation of detrimental increases in NGF appeared to be a mechanism by which migrated fetal astrocytes can be used as a system for cell therapy.

Animals↗

PubMed1993

Sequestering of immunoglobulins by astrocytes after cortical lesion and homografting of fetal cortex.

The immunoglobulin (IgG, IgM, IgA) content of normal, reactive and migrated rat astrocytes was studied in lesioned adult rat cortex and after fetal cortex grafts. Implantation pockets were aspirated in the somatomotor cortex (under bregma) of adult Sprague-Dawley rats. A fetal (E14) rat hemicortex incubated in the plant lectin Phaseolus vulgaris leucoagglutinin (graft premarker) was placed in the aspiration pocket or the pocket left empty (control). Sections of brain were immunohistochemically double labeled for immunoglobulins-GFAP or Phaseolus vulgaris leucoagglutinin-GFAP 3-60 days postoperative. Mature or fetal astrocytes in situ did not contain immunoglobulins. In pocket-only animals, individual reactive astrocytes lining and subjacent to the pocket were positive for rat IgG, IgM and IgA (3-60 days). In grafted animals, graft derived astrocytes (Phaseolus vulgaris leucoagglutinin-GFAP positive) were intermingled with host reactive astrocytes (Phaseolus vulgaris leucoagglutinin negative) lining and subjacent to the pocket. Both classes of astrocytes contained immunoglobulins IgG, IgM and IgA. Immunoglobulin positive graft derived astrocytes migrated into the corpus callosum, cingulum and habenula. These results demonstrate that astrocytes sequester immunoglobulins and probably other serum proteins as a critical function in restoring homeostasis to the injured or diseased nervous system.

Animals↗