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M L Reynolds

Publications and source records attributed to M L Reynolds.

At least 37 records · Page 2Linked to original sources
PubMed1987

Fetuin as a marker of cortical plate cells in the fetal cow neocortex: a comparison of the distribution of fetuin, alpha 2HS-glycoprotein, alpha-fetoprotein and albumin during early development.

Fetuin, alpha 2HS-glycoprotein (alpha 2HS), alpha-fetoprotein (AFP) and albumin have been shown to be present in some regions of the neocortex in two early stages of development of the cow brain using PAP immunocytochemistry. In the pre-cortical plate stage fibres of the primordial plexiform layer stained positively for fetuin. No staining was seen for albumin but plasma and cerebrospinal fluid (CSF) were positive for alpha 2HS and AFP. In the early cortical plate stage the strongest fetuin positive staining was seen in the earliest formed cells of the plate. alpha 2HS staining was much less intense but similar in distribution. The possible role of fetuin, or related glycoproteins, in cortical plate differentiation is discussed. Staining for AFP and for albumin was seen mainly in the ventricular zone and marginal zone fibres, and had a similar distribution and intensity for both proteins. Plasma and CSF stained for all four proteins. Tests showed some cross-reactivity between fetuin and anti-alpha 2HS and, to a much lesser extent, between antisera to AFP and albumin and antigens denatured by fixation.

Animals↗
PubMed1987

A fetuin-related glycoprotein (alpha 2HS) in human embryonic and fetal development.

The human plasma protein, alpha 2HS glycoprotein, has an amino acid composition very similar to that of fetuin, the major protein in fetal calf and lamb serum. Immunohistochemical studies of human fetuses (6-33 weeks gestation) showed that alpha 2HS glycoprotein and fetuin have similar distributions in developing brain and several other tissues, e.g., bone, kidney, gonads, gastrointestinal tract, respiratory and cardiovascular systems. There were notable differences in the liver and thymus in the distribution of the two proteins. Fetuin and alpha 2HS glycoprotein are present in plasma and cerebrospinal fluid of both human and sheep fetuses; their concentrations are reciprocally related: in human plasma and cerebrospinal fluid alpha 2HS glycoprotein concentration is high and fetuin low; the reverse is the case in sheep fetuses. Estimates of the concentration of alpha 2HS glycoprotein in human fetal cerebrospinal fluid and plasma were obtained. It is suggested that alpha 2HS glycoprotein may play a role in developing tissues, especially in the human fetus, similar to that of fetuin in other species.

Blood Proteins↗
PubMed1986

Tissue disposition of [3H]sarin and its metabolites in mice.

The biodisposition and metabolic fate of [3H]sarin was investigated in mice after iv administration of a sublethal dose (80 micrograms/kg). Within 1 min of administration, all tissues contained substantial quantities of radioactivity of which less than 10% represented [3H]sarin. The major portion of radioactivity corresponded to free [3H]isopropyl methylphosphonic acid (IMPA), the pharmacologically inactive hydrolytic product of [3H]sarin. Somewhat lesser quantities were present as bound [3H]IMPA which resulted from phosphorylation of protein. Plasma contained high concentrations of bound [3H]IMPA, consistent with sarin's very reactive nature, which were sustained throughout the time course. Plasma concentrations of free [3H]IMPA diminished rather quickly. The high concentrations of metabolites in kidneys implied that this organ played a major role in the detoxification and excretion of [3H]sarin. Large quantities of free and bound [3H]IMPA were also found in lung which suggested an important site for toxicity. Only trace quantities of [3H]sarin were found in brain after 15 min. The major portion of radioactivity was present as either free and bound [3H]IMPA or as nonextractable material which presumably was [3H]methylphosphonic acid. Examination of the time course of sarin-induced motor hypoactivity and hypothermia revealed an immediate onset of action that lasted for 24 hr. However, substantial quantities of bound [3H]IMPA remained in brain at 24 hr which suggested that only a small portion of phosphorylation in brain accounted for these pharmacological effects.

Animals↗
PubMed1985

Relationship between the biodisposition of [3H]soman and its pharmacological effects in mice.

The iv administration of soman (25 micrograms/kg) resulted in inhibition of cholinesterase activity in plasma, brain, and diaphragm, as well as depression of spontaneous activity and rectal temperature in mice. The motor activity and rectal temperature of these animals had returned to control levels within 24 hr, but cholinesterase activity was not fully recovered after 3 days. Following iv administration of [3H]soman (25 micrograms/kg), only trace quantities of [3H]soman were found in all tissues as early as 1 min after injection. Almost half of the injected material was present in the form of free [3H]pinacolylmethylphosphoric acid (PMPA) within 1 min of injection of [3H]soman. The concentrations of [3H]PMPA fell by more than 50% by 1 hr. High concentrations of covalently bound [3H]PMPA were present in all tissues immediately after [3H]soman treatment, particularly in lungs, heart, and kidneys. These concentrations declined slowly and after 8 hr, the quantities of bound [3H]PMPA in most tissues had fallen by less than 50%. The radioactivity in brain was identified as bound and free [3H]PMPA, nonextractable radioactivity (presumably [3H]methylphosphonic acid), and only traces of [3H]soman. It appears that phosphorylation of cholinesterase in the central nervous system is not solely responsible for depression of motor activity and rectal temperature.

Animals↗
PubMed1985

The distribution of plasma proteins in the neocortex and early allocortex of the developing sheep brain.

The histogenesis of the cerebral neocortex and early allocortex of the sheep has been described and, using an immunohistochemical technique, five plasma proteins have been identified in the telencephalic wall and their distribution followed during its differentiation. The development of the neocortex was studied from 18 days gestation, when the neural tube was still open, to 120 days, when the adult structure was established. A primordial plexiform layer was formed above the ventricular zone by 25 days and by 35 days this layer was divided by the differentiating cortical plate into an outer marginal zone and an inner subplate zone. The appearance of the subventricular and intermediate zones by 50 days gestation completed the formation of the neocortical layers. The differentiation of the allocortex was generally less advanced than the neocortex up to 40 days gestation, when the primordium of the pyramidal layer was beginning to develop. The five plasma proteins identified, fetuin, alpha-fetoprotein, albumin, transferrin and alpha 1-antitrypsin, are quantitatively the most important in the csf and plasma of the sheep fetus. Fetuin was the earliest plasma protein to be detected in the brain and it was also the most widespread; positive staining for this protein was seen in cells and fibres of all layers as they differentiated and could still be identified in some mature neurons at 120 days. alpha-Fetoprotein and albumin had a limited distribution, appearing in cells in the developing cortical plate for a short period early in gestation (35-40 days), but mainly confined to the ventricular zones later and barely detectable by 80 days gestation. Transferrin appeared to have a different distribution, being detected in fibres first in the primordial plexiform layer and then in the marginal and subplate zones, only later being identified in cells of the cortical plate. From their distribution it is suggested that fetuin and transferrin may play an important role in the differentiation of the cortex and the establishment of correct connections between fiber systems and migrating cells at certain stages of development. alpha 1-Antitrypsin was only found in a few cells during a restricted period of gestation. All five plasma proteins were identified in precipitated csf and plasma at most ages examined, although at 18 days gestation albumin, transferrin and alpha 1-antitrypsin and at 120 days, alpha-fetoprotein, could not be detected.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Postnatal development of the telencephalon of the tammar wallaby (Macropus eugenii). An accessible model of neocortical differentiation.

The sequence of development of cell layers in the neocortex of the tammar has been followed from 24 days gestation to 213 days postnatal. The tammar is born at 27 days gestation and the major period of its development occurs during the subsequent 250 days, most of this time being spent within the pouch. Although the pattern of differentiation of the cell layers appears to resemble that described for many Eutherian mammals, the neocortex is at an embryonic 2 layered stage at birth and a cortical plate is not present throughout the telencephalon until 10-15 days postnatal. A transient subplate zone, presenting a characteristic appearance with widely spaced rows of cells aligned parallel to the cortical surface, develops between 20 and 70 days postnatal, but no secondary proliferative region is seen in the subventricular zone of the dorso-lateral wall. Preliminary experiments with (3H)-thymidine injections indicate that the cortical plate follows the "inside-out" pattern of development described in many Eutherian mammals and that the oldest neurons are found in the parallel cell rows of the subplate zone. The importance of the late differentiation of the neocortex in relation to the time of birth and the resulting usefulness of the tammar as an experimental model of cortical development is discussed.

Aging↗
PubMed1985

CSF-brain permeability in the immature sheep fetus: a CSF-brain barrier.

The permeability of the neuroependyma between CSF and brain extracellular space has been studied in fetal sheep of 60 and 125 days gestation. Both radioactive ([3H]inulin, [14C]sucrose, [125I]albumin) and visible (horseradish peroxidase) markers have been perfused through the ventricular system for periods of up to 5 h in anaesthetized exteriorized fetal sheep whose physiological condition was monitored continuously. A previously undescribed barrier between CSF and brain extracellular fluid has been discovered in the immature (60-day) fetal sheep. Horseradish peroxidase penetration was confined to a limited depth of the neuroependyma and was mainly into the cells lining the cerebral ventricles; in older fetuses there was extracellular penetration to a distance of several millimetres from the ventricular surface, as previously described in adult animals. The volumes of distribution of sucrose and insulin were less in the immature brain than in the more mature brain, which may be a reflection of restricted diffusion across the neuroependyma in the younger brains. The morphological nature of the barrier in fetuses of 60 days and younger appears to be a membrane specialization between the cells of the neuroependyma. It is of a type not previously described; it seems to have the effect of narrowing rather than obliterating the extracellular pathway between CSF and brain. The possible functional significance of this observation is discussed.

Animals↗
PubMed1984

Binding of [3H]phenycyclidine to rat and human blood constituents.

The binding of [3H]phencyclidine (PCP) to rat serum and human plasma was studied using equilibrium dialysis. [3H]PCP bound with a relatively low affinity to both rat serum (KD = 1.5 X 10(-5) M) and human plasma (KD = 6.2 X 10(-6) M). However, the binding capacity was quite large for rat serum (5.7 nmoles/ml) and human plasma (5.6 nmoles/ml). Binding was readily reversible as shown by the efflux of [3H]PCP from a dialysis bag containing the rat serum-drug complex. In addition, the [3H]PCP-human serum complex appeared to dissociate completely when analyzed by Sephadex gel filtration chromatography. The low affinity of PCP for serum appeared to account in large part for the high tissue-to-plasma ratios that are observed in animals and humans injected with this drug. In vitro equilibration of [3H]PCP between rat serum and tissue homogenates resulted in at least a 10-fold accumulation of [3H]PCP in the homogenates. [3H]PCP was found to bind weakly to the major protein components of human serum (macroglobulins, immunoglobulins and albumins). The weak nature of the binding to serum proteins coupled with the relatively high capacity of binding probably account for the failure of other drugs to compete for PCP binding.

Animals↗
PubMed1984

Differential immunocytochemical staining for fetuin and transferrin in the developing cortical plate.

The distribution of the plasma proteins fetuin and transferrin in fetal sheep neocortex has been studied using the indirect immunoperoxidase method. Most of the cells (presumed to be neurons) in the early cortical plate (35 days gestation) were positive for fetuin. In contrast the fibre systems on either side of the cortical plate were positive for transferrin; some fibres were weakly positive for fetuin. It is proposed that these fibres may originate from brainstem and perhaps from some thalamic nuclei and that the plasma proteins are probably transferred from the neuronal cell bodies to their peripheral processes. It is further suggested that plasma proteins such as fetuin and transferrin may have a role in neuronal differentiation and synaptogenesis.

Animals↗
PubMed1983

The distribution of plasma proteins during early embryonic development in the sheep.

The distribution of the five plasma proteins that are quantitatively most important during development in the sheep has been studied in embryos of 15 to 21 days gestation. The three primary embryonic layers and tissues that differentiate from them were tested for the presence of alpha-fetoprotein (AFP), fetuin, albumin, transferrin and alpha 1-antitrypsin using the indirect immunoperoxidase method. Fetuin was the most prominent of these proteins particularly in the developing central nervous system. Fetuin and transferrin appeared early in the differentiating mesoderm and, with albumin and AFP, were detected in tissues originating from all three layers during the course of development. alpha 1-Antitrypsin appeared to have a limited distribution. All five plasma proteins were detected before the establishment of a circulatory system. It is suggested that their appearance in embryonic tissue is related to its stage of development and that they play an important part in early differentiation.

Albumins↗
PubMed1983

Comparison of proteins in CSF of lateral and IVth ventricles during early development of fetal sheep.

This study examines the relationship between plasma proteins in blood and in CSF in the developing brain of sheep fetuses between 30 and 60 days gestation. Five proteins account for the very high concentration of protein in fetal CSF (over 1000 mg/100 mg/100 ml at 30 days): alpha-feto-protein, fetuin, albumin, alpha 1-antitrypsin and transferrin; the concentration of each protein is similar in lateral and IVth ventricular CSF at 30 days. By 40 days there is considerable decrease in protein concentration in lateral ventricular CSF. At this age in the IVth ventricle the overall total was unchanged, although there were changes in concentration of individual proteins. At 60 days the concentration of each protein in both compartments had fallen below that at 40 days; the marked concentration difference between lateral and IVth ventricular CSF was still present. Experiments using i.v. [125I]- or [3H] labeled plasma proteins in 30-40-day fetuses showed that very little protein penetrated into lateral ventricular CSF by 3-5 h after injection; in the same experiments [125I]albumin reached a CSF/plasma ratio of about 15% in the IVth ventricle (compared with 55% for the natural steady state). Autoradiographic studies carried out on material from the same animals did not give evidence for transfer of labeled protein across the choroid plexuses although any such penetration may have been below the threshold of the method. Other explanations for the high concentration of protein in CSF that were considered include penetration via cerebral vessels and synthesis of plasma proteins by choroid plexus epithelial cells or neurons within the brain.

Albumins↗
PubMed1981

Plasma proteins in fetal sheep brain: blood-brain barrier and intracerebral distribution.

1. Plasma proteins have been demonstrated to be present in early fetal sheep brain in amounts which cannot be accounted for by blood contamination. 2. The distribution of alpha-fetoprotein, albumin, fetuin, alpha 1-antitrypsin and transferrin has been studied by immunoassay of extracts from brain homogenates and by immunoperoxidase histochemistry of fetal brains between 37 and 125 days gestation (term is 150 days). 3. At 35 days gestation fetuin and albumin were quantitatively the most important proteins in fetal brain, both as estimated by extraction and by immunohistochemistry. Both of these proteins, and also alpha-fetoprotein and alpha 1-antitrypsin, declined considerably in amount by 60 days gestation. After 60 days the concentrations of albumin and alpha-fetoprotein were not significantly different from that due to blood contamination and only occasional cells could be demonstrated by immunohistochemistry. Fetuin and alpha 1-antitrypsin were present in reduced but significant amounts at least up to 125 days gestation. 4. The immunohistochemical results showed that considerable numbers of immature neurones were stained for some plasma proteins. Fetuin positive cells predominated both in terms of the larger number of cells which stained at 35-40 days gestation and in the persistence of positive cells up to 125 days gestation. Numerous cells in the neuroependymal layer and in several layers of the developing cortical plate were positive, especially early in gestation. Only a few transferrin or alpha 1-antitrypsin positive cells were observed. 5. Permeability of the blood-brain barrier to sheep or human serum albumin (labelled with 125I) was tested in 60 day fetal sheep by intravenous injection and estimation of brain radioactivity at 3 or 6 hr with allowance for blood contamination. Only a very small (but significant) penetration of protein was detected. Unlike penetration of protein into c.s.f. at the same age, it did not reach its natural steady state in brain. 6. It is concluded that the blood-brain barrier to protein is well developed in the immature fetal sheep but that developing neurones probably acquire certain plasma proteins directly from the c.s.f. when they are differentiating in the neuroependyma. The subsequent distribution of plasma protein positive cells in different brain regions is suggested to be due to the migration of developing neurones for the neuroependyma although the possibility of local synthesis of plasma proteins has not been excluded.

Albumins↗
PubMed1980

Proteins in cerebrospinal fluid and plasma of fetal sheep during development.

1. The concentration of total protein in c.s.f. and plasma has been measured in fetal sheep of different gestational ages and in the adult. In c.s.f. it was highest (approximately 840 mg/100 ml.) in the youngest fetuses (35 days) and declined steeply by 60 days (260 mg/100 ml.). It decreased less markedly in the last half of gestation to reach about 50 mg/100 ml. at 125 days which is twice the adult value. Protein concentration in plasma was lowest in the youngest fetuses and did not rise much until the second half of gestation during which time it doubled. There was a further rather larger increase between the late fetal (125 days) stage and the adult.2. Albumin, fetuin, alpha-fetoprotein (AFP), transferrin and lipoprotein were identified in c.s.f. and plasma.3. The concentrations of albumin, AFP and fetuin in c.s.f. and plasma at different gestational ages were measured using immunodiffusion and radioimmuno-assays.4. Albumin was the major protein in plasma at all ages studied (35-128 days gestation and adult). Its concentration increased throughout gestation whereas that of fetuin was similar at all fetal ages and that of AFP declined markedly during the second half of gestation. In the adult, fetuin was only about 0.1% of the total protein in plasma and AFP was not detectable.5. In 35-40 day fetuses albumin, AFP and fetuin accounted for 90% of the total protein concentration in plasma and for about 70-80% of the total protein concentration of c.s.f. As gestation progressed the concentration of all three proteins in c.s.f. declined. But the concentration of AFP and fetuin fell more rapidly and to a greater extent than that of albumin; neither AFP nor fetuin could be detected in adult c.s.f.6. The c.s.f.: Plasma ratio was above 50% for AFP and above 60% for fetuin at 35 days compared with about 25% for albumin at the same fetal age. The c.s.f.: plasma ratios for all three proteins declined with increasing fetal age and were not significantly different from each other by about mid gestation.

Albumins↗
PubMed1980

Blood-cerebrospinal fluid transfer of plasma proteins during fetal development in the sheep.

1. The penetration of human and sheep plasma proteins from blood into c.s.f. of sheep fetuses (57-86 days gestation) has been studied. The proteins were injected intravenously via cotyledonary vessels. After different time periods the c.s.f. concentrations of marker proteins were estimated by radioactive counting of iodinated human or sheep proteins or by immunoassay of human proteins.2. Several proteins of similar molecular size penetrated into c.s.f. to a different extent in 60 day fetuses. The steady-state c.s.f.: plasma ratios were about 15% for human AFP, 10% for human transferrin and sheep albumin, 7% for human alpha(1)-antitrypsin, and 5% for human albumin. In older fetuses the penetration of protein from blood into c.s.f. was much reduced and no evidence for differential penetration of different proteins was found.3. The penetration of human AFP, transferrin and sheep albumin from blood into c.s.f. was greater than can be accounted for by passive diffusion.4. The results of this paper are discussed in relation to those of the preceding paper on the identification and quantification of proteins in fetal c.s.f. and plasma. The hypothesis is put forward that the choroid plexus of the immature (60 days and less) sheep fetus contains a mechanism for the transcellular transfer of plasma proteins which may be selective in nature and of importance for some aspects of brain development.

Albumins↗
PubMed1979

Intracranial haemorrhage in the preterm sheep fetus.

The germinal layer in the brain of the sheep fetus at 58--85 days of gestation was found to resemble that of the human infant at 28--30 wk of gestation. Experiments were done on 65 exteriorized fetuses to explore the effect of various combinations of asphyxia and raised intravascular pressures in causing bleeding into the germinal layer, ventricles and other parts of the brain. Asphyxia by itself did not produce an increase in the incidence of intracranial hemorrhages when compared with control fetuses. The combination of asphyxia with intermittent increases in arterial or venous pressure, or both, did cause haemorrhages. Large increases in arterial pressure without asphyxia also caused intracranial haemorrhages, whereas increases in venous pressure without asphyxia did not. The types of haemorrhage observed closely resembled those seen in the preterm human infant, although massive intraventricular haemorrhages (IVHs) were rare. We conclude that: (1) the sheep fetus can be used for investigating factors associated with intracranial haemorrhage in the preterm brain; (2) the most effective method of producing haemorrhages into the germinal layer was by a combination of asphyxia with intermittent increases in cerebral intravascular pressure. Similar mechanisms may be at work in the newborn human infant, and could lead to IVH.

Animals↗
PubMed1979

Studies of the development of brain barrier systems to lipid insoluble molecules in fetal sheep.

1. The development of the blood-brain and blood-c.s.f barriers to lipid insoluble substances of different molecular radii has been studied in fetal sheep, early (60 days) and late (125 days) in gestation, using labelled erythritol (C14), sucrose (3H or 14C), inulin (3H or 14C) and albumin (125I), or albumin and IgG detected by immunoassay. 2. Morphological studies of fetal brain and choroid plexus at the same gestational stages were carried out using thin section electron microscopy and the freeze fracture techniques. 3. Penetration of markers into c.s.f. was substantially greater at 60 days than at 125 days, but at both ages the steady-state level achieved appeared to be related to molecular size. 4. A simple model describing penetration from blood into c.s.f. at 60 days is proposed. It involves the assumption that c.s.f. and brain extracellular fluid are effectively separate compartments; morphological and permeability data which supports this assumption is presented. The data for c.s.f. at 60 days are consistent with the suggestion that the markers penetrate into c.s.f. by diffusion and are not restricted by small pores in the interface between blood and c.s.f. 5. The reduction in penetration which occurred by 125 days for all markers except erythritol appears to be accounted for by an increase in the sink effect and a decrease in the effective surface area for exchange between blood and c.s.f. 6. Intercellular tight junctions of both cerebral endothelial cells and choroid plexus epithelial cells were well formed at 60 days gestation. There was no change in junctional characteristics previously thought to correlate with transepithelial permeability (tight junction depth and strand number) between the two ages studied, although there were marked changes in permeability. 7. Evidence is advanced in support of the hypothesis that in the fetus much of the penetration of lipid insoluble non-polar substances across the blood-c.s.f. barrier and perhaps across the blood-brain barrier occurs via a transcellular route consisting of a system of tubulo-cisternal endoplasmic reticulum. Penetration via the choroid plexus appears to be the dominant route for penetration from blood into c.s.f. in the 60 day fetus.

Animals↗