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Biomedical subjects

J A Jackson

Publications and source records attributed to J A Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1994

Infrapopulation dynamics of Gyrdicotylus gallieni (Monogenea: Gyrodactylidae).

Gyrdicotylus gallieni is a viviparous gyrodactylid monogenean that infects the buccal cavity and pharynx of Xenopus laevis laevis. Offspring directly recolonize the same host as their parent and transmission is carried out exclusively by adult worms which are capable of leech-like stepping locomotion. The infrapopulation dynamics (at 20 degrees C) of this species were studied by experimental exposure to single worms of previously uninfected hosts (which were dissected at various time-intervals post-infection). Infrapopulations increased exponentially until 50 days post-infection (p.i.), during which time the intrinsic rate of increase was estimated by regression as 0.065/parasite/day. After this, infrapopulation sizes showed greater variability, with established infections becoming extinct 2-5 months p.i.: elimination was probably due to some form of host reaction, as parasite lineages were maintained for up to 10 months by transfers to successive uninfected hosts. The development of infrapopulations is similar to that reported for other viviparous gyrodactylids parasitic on the body surface of teleosts. However, the intrinsic rate of increase was comparatively slow in G. gallieni and the duration of infection in isolated hosts prolonged. Slow-growing infrapopulations may elicit a host response more slowly and extend the period during which dispersal to a new host or host population can occur. This might be important in G. gallieni for which the internal site of infection could limit the transmission rate, as worm migration from the oral cavity or accidental detachment and expulsion is necessary for host-host transfer to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Continuous measurement of lumbar posture using flexible electrogoniometers.

Continuous measurement of changing limb segment angle is possible using a recently introduced flexible electrogoniometer but, unfortunately, the magnitude of linear displacements occurring during flexion and extension of the trunk has prevented its use as a measure of spinal mobility and posture. To overcome this limitation, a specially constructed, lightweight, aluminium carriage has been developed to allow free linear travel of the electrogoniometer, while maintaining the angle recorded between the thoracolumbar junction and the sacrum. The reliability and practicability of this new approach for recording changes in lumbar posture have been investigated. Following bench tests and operator training, measurements of maximal flexion and extension of the lumbar spine were repeated on 12 subjects. The extent of sagittal mobility was compared with measures from a fluid-filled inclinometer and a flexicurve. Analysis of the data showed that the use of the aluminium carriage did not markedly influence the accuracy of the electrogoniometer, and the technique as modified was found to be comparable with standard techniques for estimating the extent of lumbar sagittal flexibility. A field based study, involving four garage mechanics, was undertaken to examine the usability and acceptability of the electrogoniometer technique for continuous measurements. Lumbar curvature was monitored continuously for a two hour period during the course of the mechanics' working day. Dedicated software provided angle-time plots from which it was established that extreme flexed or extended postures were maintained only for relatively short periods; projection to an eight hour shift would indicate that a total of approximately 40 min is spent in extension beyond 10 degrees and flexion beyond 50 degrees. The technique has the potential to provide quantitative information on lumbar posture necessary for non-invasive, biomechanical investigations of spinal loading. It will be particularly useful for both sporting and occupational ergonomics field-studies.

Adult↗
PubMed1994

Chemical characterization and disposition studies with 1,2,7,8-tetrabromodibenzofuran in the rat.

Polybrominated dibenzo-p-dioxins and dibenzofurans have been identified as potential environmental contaminants. The present studies were designed to characterize the chemical disposition of a tetrabrominated dibenzofuran. The isomer-specific pattern of 1,2,7,8-tetrabromodibenzofuran (TBDF) was chemically characterized using high-pressure liquid chromatography, gas chromatography/mass spectrometry, infrared absorption, and proton nuclear magnetic resonance techniques. The absorption, distribution, and elimination of 1,2,7,8-[4,6-3H]-TBDF were examined in the rat following a single oral, dermal, or intravenous dose of 1 nmol/kg. The 1,2,7,8-TBDF was rapidly excreted in the bile (approximately 50% of the dose in 8 h). Likewise, over half of the administered dose was found in the feces and intestine contents 24 h after iv administration and in feces 72 h after oral administration. Thus, the half-life of 1,2,7,8-TBDF is approximately 1 d. Major tissue depots included the liver, adipose tissue, and skin. The decline in hepatic concentrations observed in the iv and bile studies occurred in conjunction with metabolic elimination as well as a slight accumulation in adipose tissue. Dermal absorption of 1,2,7,8-TBDF, quantified as the amount contained in tissues (excluding the skin site) and excreta at 72 h, was estimated to be 29% of the administered dose. Thus, the general disposition profile of 1,2,7,8-TBDF in the rat is similar to that of other polyhalogenated aromatic hydrocarbons. Due to its rapid elimination, which is consistent with its predicted susceptibility to metabolic elimination, acute exposure to 1,2,7,8-TBDF would not be expected to result in the degree of toxicity associated with other more persistent congeners.

Absorption↗
PubMed1994

Plasminogen activator production by the granulosa layer is stimulated by factor(s) produced by the theca layer and inhibited by the luteinizing hormone surge in the chicken.

The stages of follicular maturation of a preovulatory follicle in the hen can be divided into an extended proliferative phase (prior to LH surge) and a brief ovulatory phase (after LH surge). Previous studies suggest involvement of plasminogen activator (PA) in both the proliferative and ovulatory phases. The goals of the present study were 1) to determine whether PA production by granulosa and theca is dependent upon interaction of the two cell layers; 2) to investigate whether the structural difference of the stigma (site of follicular rupture) and nonstigma regions of the theca layer affect PA production; 3) to determine whether there is a change in the ability of the granulosa layer and stigma or nonstigma regions of the theca layer to produce PA as the follicle makes the transition from the proliferative to the ovulatory phase; and 4) to characterize the type(s) of PA produced by the hen follicle. Equal proportions of the granulosa layer (10-mm diameter) and stigma or nonstigma regions of the theca layer (10 mg) obtained from the F1 preovulatory follicle 8 h before ovulation (before LH surge) or 2 h before ovulation (after LH surge) were incubated alone or in combination for 24 h. PA was measured in tissue homogenates and medium by use of the chromogenic substrate S-2251. The granulosa layer or stigma or nonstigma regions of the theca layer incubated alone and obtained either 8 h or 2 h before ovulation had very low amounts of PA activity in the medium and tissue homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Body temperature changes before minor illness in infants.

This study aimed to examine the overnight temperature pattern of babies during the prodromal phase of minor illnesses. The overnight rectal temperature pattern of 123 babies was recorded weekly from about 6 to at least 16 weeks old, while parents maintained detailed records of signs of illness. By analysis of patterns of signs and visits to the general practitioner, 86 periods of minor illness were identified, mostly upper respiratory tract infections, though it was not usually possible to identify the infection by conventional virology. Data were analysed separately for babies who had developed an adult-like night time temperature pattern and those who had not. In both groups, obvious signs of illness were preceded by a disturbance of night time temperature pattern. Temperature was significantly raised over control weeks, though few babies were clinically febrile. The greatest temperature disturbances were seen in the three days before illness, though some disturbances were seen up to seven days before. A similar disturbance of temperature was seen the night after diphtheria, pertussis, and tetanus immunisation, and individual responses to natural infection and immunisation were well correlated, suggesting that the temperature change is more a function of the host response than the infecting agent.

Body Temperature↗
PubMed1994

Calcium and cation-anion balance effects on feed intake, body weight gain, and humoral response of dairy calves.

Our objective was to examine whether feeding low cation-anion diets altered the Ca status of the growing calf. Holstein calves (n = 32; 16 males) were blocked at 56 to 70 d after birth according to sex and birth date and assigned randomly to dietary treatments containing Ca content and cation-anion balances as milliequivalents of (Na+K)-(Cl+S)/100 g of dietary DM of .42% and -18, .52% and -18, .42% and 13, and .52% and 13. Feed intake did not differ among treatments. Calves fed the diet with cation-anion balance of 13 had higher gain (.85 vs. .71 kg/d) than those fed the diet with balance of -18. Venous blood pH (7.374 vs. 7.323), partial pressure of CO2 (47.9 vs. 45.6 mm Hg), and bicarbonate (28.3 vs. 23.3 mmol/L) were higher for calves fed the 13 versus -18 balances. Plasma Ca and P were unaffected by Ca or cation-anion balance. Urinary pH was higher for calves fed the high than the low balance (7.442 vs. 6.047). Urinary Cl and Ca excretion was higher for calves fed the low than the high balance. Breaking strengths for 7th and 9th ribs were higher for calves fed the high balance and higher for the 7th rib only for calves fed the high Ca diet. Cation-anion balance altered Ca metabolism, but it is unclear whether Ca requirements were also altered.

Acid-Base Equilibrium↗
PubMed1993

Estimation of octanol-water partition coefficients and correlation with dermal absorption for several polyhalogenated aromatic hydrocarbons.

n-Octanol-Water partition coefficients (K(ow)) were experimentally estimated for: 2,3,7,8-tetrachloro-and 2,3,7,8-tetrabromodibenzo-p-dioxin; 2,3,7,8-tetrachloro-, 2,3,7,8-tetrabromo-, and 1,2,7,8-tetrabromodibenzofuran; 1,2,3,7,8-pentachloro-, 1,2,3,7,8-pentabromo-, 2,3,4,7,8-pentachloro-, and 2,3,4,7,8-pentabromodibenzofuran; 1,2,4,6,8,9-hexachlorodibenzofuran (HxCDF), and 3,4,3',4'-tetrachlorobiphenyl (3,4,3',4'-TCB). The method involved correlation of literature K(ow) with reverse-phase high-performance liquid chromatography (RP-HPLC) retention time for a series of 23 calibration standards and estimation of K(ow) for test compounds from measured RP-HPLC retention. Retention times for all standards and test chemicals were measured in duplicate on the same octadecasilane (C18) reverse-phase column with an isocratic 85:15 methanol:water mobile phase; solutes were detected by uv absorbance (254 nm). Literature log K(ow) values used for the calibration standards had been measured exclusively by the generator column method. Log K(ow) estimates for the test compounds in the present study ranged from 5.45 for 3,4,3',4'-TCB to 6.81 for HxCDF. K(ow) estimates were then plotted against laboratory data for the in vivo 3-day dermal absorption of single equimolar doses (200 pmol and 20 nmol, or approximately 1 nmol/kg and approximately 0.1 mumol/kg) of selected test compounds in male F344 rats. Strong inverse correlations were found between octanol-water partition coefficient estimates and single-dose dermal absorption for most of the compounds studied. In addition, RP-HPLC retention time itself appeared to be as equally suited as K(ow) to such correlations with dermal absorption. The structure-activity relationships suggested in this study were sought in order to explain observed differences in the dermal absorption of polyhalogenated dibenzo-p-dioxin, dibenzofuran, and biphenyl congeners differing in number, position, and/or type (Cl or Br) of halogen substituents. Moreover, these results should be of predictive value in the risk assessment of dermal exposure to polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls, and their brominated analogues.

Animals↗
PubMed1993

Maturational changes in dermal absorption of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Fischer 344 rats.

An earlier study indicated that percutaneous absorption of a 40-nmol dose of TCDD decreased with aging in rats, suggesting that the potential for systemic exposure following dermal contact would be decreased in older age groups. In this study, maturational changes in potential for systemic exposure to TCDD following dermal application of a low dose (200 pmol) of this chemical were examined in male Fischer 344 rats. Absorption, tissue distribution, and elimination of TCDD, measured as TCDD-derived radioactivity, were examined 72 hr after dermal application of 200 pmol [3H]TCDD (111 pmol/cm2 applied over 1.8 cm2) to the interscapular region of 3-, 5-, 8-, 10-, and 36-week-old rats. The dose was applied in 60 microliters acetone and the application site was covered with a perforated metal cap; animals were held in individual metabolism cages. Dermal absorption was greatest in 3-week-old rats (approximately 129 pmol; approximately 64% of the administered dose), decreasing to approximately 80 pmol (approximately 40%) in 5-, 8-, and 10-week-old rats and to 45 pmol (approximately 22%) in 36-week-old rats. In each age group, 70 to 80% of the radioactivity remaining at the application site 72 hr after dosing could be removed with acetone swabs. Major tissue depots of radioactivity were liver and fat; skin and muscle were minor depots. Changes in distribution of absorbed TCDD-derived radioactivity reflected changes in body mass of these depots; however, tissue concentration also varied. Whole body dissection was performed on rats to determine body mass of tissue depots. Adipose tissue content (Y) increased linearly with body weight (X), Y = 0.03X + 2.1 (r2 = 0.95). Elimination of absorbed TCDD-derived radioactivity was incomplete in all age groups with larger residues being recovered in the carcass. Results indicate that TCDD is absorbed to a greater degree through skin of very young animals and that a significant decrease in potential for systemic exposure may occur during maturation and again during aging.

Administration, Cutaneous↗
PubMed1993

Effects of dose and routes of exposure on the disposition of 2,3,7,8-[3H]tetrabromodibenzo-p-dioxin (TBDD) in the rat.

Polybrominated dibenzo-p-dioxins and dibenzofurans are of major concern because of potential occupational and environmental exposures and their structural similarity to the highly toxic chlorinated analogues. 2,3,7,8-Tetrabromodibenzo-p-dioxin (TBDD) is a closely related analogue in both structure and activity to the most toxic isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin. The objectives of this study were to characterize the effects of dose and routes on absorption, excretion, and terminal tissue distribution of [3H]TBDD in the rat 72 hr after dosing. Rats were treated orally by gavage with 1, 10, 100, or 500 nmol/kg, intratracheally with 1 nmol/kg, or dermally with 1 nmol/kg (200 pmol/1.8 cm2). TBDD exhibited nonlinear oral absorption kinetics with maximum absorption (approximately 80%) occurring at dose < or = 10 nmol/kg, similar to the transpulmonary absorption. In contrast, dermal absorption of TBDD was low (approximately 12%). The major tissue depots of radioactivity were liver, adipose tissue, and skin. Tissue distribution of the oral dose was dose-dependent, with disproportionally greater hepatic concentrations occurring at absorbed doses of > 8 nmol/kg. Liver:adipose tissue (L:F) concentration ratios were 2.9 to 6.6 (lowest to highest oral dose, respectively). The lower L:F ratios observed for the dermal and intratracheal doses at 1 nmol/kg (1.5 and 2, respectively) were likely due to differences in absorbed dose and dose-related tissue distribution. Elimination of radioactivity in feces, the major route of excretion for all dose groups and routes, and urine was also nonlinear with respect to the oral dose. The results of the present study provide important considerations for high- to low-dose and route-to-route extrapolations with TBDD and other dioxins and furans in human risk assessments.

Administration, Cutaneous↗
PubMed1993

Plasminogen activator activity in preovulatory follicles during the ovulatory cycle of the chicken.

The stages of follicular maturation of a preovulatory follicle in the chicken can be divided into an extended proliferative phase (prior to the LH surge) and a brief ovulatory phase (after the LH surge). There is evidence to suggest that plasminogen activator (PA) may play a role in follicular maturation and ovulation in the chicken. The objective of this study was to determine whether PA activity changes in the stigma (site of follicular rupture) and nonstigma regions of the theca layer, granulosa layer, and germinal disc region (germinal disc and adjacent granulosa cells; GDR) during the transition from the proliferative phase to the ovulatory phase and immediately before ovulation. The largest preovulatory follicle (F1) and the second-largest follicle (F2), which would have ovulated first and 26 h later, respectively, were collected at 8 h and 2 h before ovulation (before and after the LH surge, respectively), and at 0.5 h (immediately before ovulation). PA activity in the stigma region of the theca layer in the F1 and F2 follicles was very low at 8 h before ovulation (before the LH surge) and increased dramatically (9-fold) at 2 h before ovulation (after the LH surge). PA activity in the stigma region of the F1 follicles remained high as the follicles prepared to ovulate (0.5 h before ovulation), whereas in the stigma region of the less mature F2 follicles it decreased to a level similar to that measured 8 h before ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Platelet-derived growth factor regulation of fos stability correlates with growth induction.

A brief exposure of quiescent, density-arrested Balb/c 3T3 fibroblasts to platelet-derived growth factor (PDGF) results in expression of the proto-oncogene c-fos; furthermore, the translation product of c-fos, p55fos, was shown to have increased stability in cells upon continued exposure to PDGF. The induction of competence or growth initiation requires a longer exposure to PDGF than that necessary for the induction of the immediate-early, growth-related genes. The need for the continued presence of PDGF for growth initiation beyond the time required for the induction of immediate-early gene expression may be due, in part, to PDGF-dependent post-translational stabilizations of gene products. We speculate that a PDGF-mediated event increases p55fos stability, resulting in a continued elevated level of Fos protein, which in turn allows a continued Fos-mediated activity required by Balb/c 3T3 cells to become competent to enter the cell cycle.

3T3 Cells↗
PubMed1992

Testosterone deficiency as a risk factor for hip fractures in men: a case-control study.

The objective of this study was to determine whether decreased gonadal function is a risk factor for hip fracture in elderly men. The study was a matched case-control study performed at an in-hospital orthopedic service at a semi-rural and academic tertiary care center. The patients were seventeen men who presented with hip fractures after simple falls over a 10-month period, 11 men with a history of hip fractures in the preceding 25 months, and 28 randomly selected age-, race-, and living status-matched control subjects (mean age 73 years). Serum pooled total testosterone (9.2 +/- 5.5 nmol/L vs. 12.8 +/- 5.4 nmol/L; p less than 0.02) and free testosterone (37.9 +/- 18.8 pmol/L vs. 48.4 +/- 20.6 pmol/L; p less than 0.03) were significantly lower in hip fracture vs. control patients. Testosterone deficiency was found in 20 (71%) hip fracture men vs. 9 (32%) of the controls (p = 0.003; odds ratio 5.3). Analysis of testosterone values within the stratum of absence of any chronic disorder revealed similar results. Serum 25-hydroxyvitamin D levels were significantly lower in the hip fracture group than in control men (p less than 0.001). The conclusion is that gonadal deficiency appears to be an important and heretofore understudied risk factor for hip fractures in men. Prevention of hip fractures in men may involve early recognition and treatment of testosterone deficiency.

Aged↗
PubMed1992

Inhibition of bovine retinal microvascular pericyte proliferation in vitro by adenosine.

Adenosine acts on bovine retinal microvascular pericytes through one or more adenosine receptor subtypes present on the cell surface. Retinal pericytes cultured in medium containing adenosine at concentrations from 10(-6) to 10(-4) M showed significant reduction in proliferation following several days in vitro compared with control cultures. The effects of adenosine were mimicked by polyadenylic acid and inhibited by 8-phenyltheophylline, indicating involvement of a cell surface receptor. Metabolites of adenosine had no effect on pericyte proliferation. An A2 adenosine receptor-specific analogue also inhibited pericyte growth, suggesting that inhibition by adenosine is mediated by A2-receptors and might involve a transient increase in adenosine 3',5'-cyclic monophosphate levels. The results of the present study demonstrate that in addition to demonstrated stimulatory effects on capillary endothelial cells, adenosine also has a direct inhibitory effect on retinal pericytes. We hypothesize a dual function of adenosine within the capillary wall resulting in loss of inhibition of endothelial cells and suggest a role for this nucleoside in pathological neovascularization processes such as proliferative diabetic retinopathy.

Adenosine↗
PubMed1992

Influence of cation-anion balance on feed intake, body weight gain, and humoral response of dairy calves.

The objective of this study was to examine the influence of diets with varying cation-anion balance on performance and humoral responses in young, growing dairy calves. Twenty-eight Holstein and 4 Jersey female calves were blocked at 56 to 70 d after birth according to breed and age and assigned randomly to dietary treatments of 0, 21, 37, and 52 meq(Na + K) - Cl/100 g of dietary DM. Diets were based on cracked corn, dried brewers grains, and oats and were fed for 8 wk. Feed intake and average daily gain tended to increase quadratically, being highest for calves fed the +37-meq diet and lowest for those fed the 0-meq diet. Blood and urine pH increased linearly with increasing dietary cation-anion balance. Plasma Ca increased linearly, and Mg and Cl decreased linearly with increasing cation-anion balance. Plasma Na and P were unaffected by dietary treatments. Urinary Ca, Mg, and Cl excretions decreased linearly; urinary P, Na, and K excretion increased linearly with increasing dietary cation-anion balance. Blood pH increased linearly with increasing dietary cation-anion balance. Blood partial pressure of CO2 and HCO3 increased concurrently with increasing dietary cation-anion balance. Results indicate that altering cation-anion balance may impact DMI and average daily gain in the young ruminant.

Animal Feed↗
PubMed1992

The cardiovascular capacities of adults with Down syndrome: a comparative study.

The purpose of this study was to compare the cardiovascular capacities of individuals with Down syndrome (DS) to individuals without Down syndrome who are mentally retarded. Sixteen young adults with DS and 16 individuals without DS (12 males and 4 females, respectively), all with mild/moderate mental retardation, participated in this study. Peak VO2 (absolute and relative), VE (1.min-1), heart rate (HR, b.min-1), and RER (VCO2/VO2) were determined by exercise tests utilizing a treadmill (TM) and Schwinn Air-Dyne ergometer (SAE). The best test result was chosen from the TM and SAE tests and used for statistical comparisons. Cardiac output (Q, 1.min-1) was measured while standing quietly and while walking at 3 mph, 0% grade, using the CO2 rebreathing method for 11 (9 males and 2 females) subjects from each group. Arteriovenous oxygen differences (a-v O2), cardiac index (QI), and stroke volume (SV) were calculated from VO2, Q, HR, and body surface area. Peripheral vascular resistance (PVR), left ventricular work index (LVWI), and left ventricular stroke work index (LVSWI) were calculated from mean arterial pressure, Q, QI, and stroke volume index. Results showed that individuals without DS had statistically significant (P less than 0.01) higher mean peak VO2 (35.6 vs 24.6 ml.kg-1.min-1; 2567 vs 1683 ml.min-1), VE (89.3 vs 59.2 1/min-1), and HR (179 vs 159 b.min-1) than individuals with DS, respectively. No differences in RER were seen between the groups. No differences were seen in cardiovascular parameters measured while quietly standing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Renin-secreting juxtaglomerular tumor causing severe hypertension: diagnosis by computerized tomography-directed needle biopsy.

Renin-secreting tumors are a rare cause of severe hypertension accompanied by hypokalemia. Typically, these tumors have been difficult to diagnose preoperatively by standard radiographic and hormonal studies. We describe a 44-year-old man who was hospitalized for paroxysmal hypertension and who had a 2.3 cm. mid upper pole renal mass on sonography. Computerized tomography-directed needle biopsy revealed a juxtaglomerular tumor and surgical excision of the tumor was curative. We discuss the unique diagnostic aspects of this case.

Adult↗
PubMed1991

Preovulatory changes in glycosaminoglycans and collagen content in the stigma region of the follicle of the domestic hen.

The present study determined the amount and types of glycosaminoglycans and collagen concentrations in follicles of the domestic hen. The stigma (S; the area of follicular rupture) and nonstigma (NS) regions of the theca layer were isolated from the preovulatory follicle (F1) and an immature follicle (F2) that were to ovulate 30 min and 26 h later, respectively. Glycosaminoglycan density, which was estimated by measuring follicular uronic acid concentration (micrograms/mg dry wt), was lower (p less than 0.01) in F1S (2.6 +/- 0.1) compared to F1NS (3.4 +/- 0.2), F2S (3.4 +/- 0.1), and F2NS (3.4 +/- 0.1). Theca glycosaminoglycans consisted of approximately 58% dermatan sulfate, 20% heparan sulfate, and 22% hyaluronic acid. The F1S contained lower (p less than 0.05) amounts of dermatan sulfate and hyaluronic acid compared to F1NS, F2S, and F2NS. There was no significant difference in amounts of heparan sulfate in the F1S, F1NS, F2S, and F2NS. Collagen density, which was estimated by measuring follicular hydroxyproline concentrations (micrograms/mg dry wt), were lower (p less than 0.01) in F1S (20.3 +/- 1.4) and F2S (19.8 +/- 1.4) compared to F1NS (28.9 +/- 1.9) and F2NS (29.9 +/- 2.7). However, there was not a further decrease in collagen concentration in the F1S compared to F2S. We suggest that glycosaminoglycans may be degraded specifically in the stigma region of the preovulatory follicle prior to ovulation. The lower amount of collagen in the stigma region may decrease the tensile strength in the stigma compared to the nonstigma region regardless of maturational stage.

Animals↗