Is dihydrotestosterone a cause of follicular atresia?

Dihydrotestosterone, a non-aromatizable androgen has been hypothesized to arrest follicular growth. The concentration of androgens in the prepubertal, adult and pregnant mammals leads one to presume that high levels of estrogens cause follicular growth and ovulation while increase in DHT results in follicular atresia. However, DHT probably has no definitive role to play during lactation and menopause. In polycystic ovarian syndrome, inhibition of normal follicular growth may be due to increased DHT secretion.     

Aflatoxin B1 effects on ovarian follicular growth and atresia in the rat

For this investigation, 28 female healthy adult Wistar rats were selected. The animals were divided into four groups (n?=?7 per group): control, test group 1, test group 2 and test group 3. Each rat in test groups 1, 2 and 3, received 0.8 ppm, 1.6 ppm and 3.2 ppm aflatoxin B1 (AFB1), respectively, via gavage for a period of 25 days. The control group received distilled water only. All tissue specimens were processed for routine paraffin embedding and serial cross-sections cut at 5–7 μm and stained with haematoxylin–eosin. Both histomorphologic and histomorphometric analysis was performed under light microscopy. An increase in the concentration of AFB1 resulted in a reduction in the population of healthy primordial, primary, secondary and tertiary follicles. The greatest reduction was in seen in group 3 (with 3.2 ppm AFB1/day). In all test groups, due to an increase in AFB1 concentration, in both the right and left ovaries, all types of atretic follicles, including primordial, primary, secondary, and tertiary atretic follicles were significantly increased (P?<?0.01). In conclusion, AFB1 is toxic for all type of ovarian follicles, including non-growing and growing follicles and exerts an atretogenic effect on all types of ovarian follicles. The atretogenic effect of AFB1 is dose dependant. Due to its toxic effects (gametotoxicity), the resting pool of ovarian follicles (primordial follicles) decreases significantly. The ovulatory follicular population either decreases or is completely depleted.     

Histological observation of the development of follicles and follicular atresia in immature rat ovaries

To clarify the development of follicular growth and atresia in the immature ovary, rats. ovaries and blood were removed at fixed points during the period from 0 to 35 days after birth (Day 0 to Day 35). The ovaries were immunohistochemically examined, and blood concentrations of serum follicle-stimulating hormone (FSH) and estrogen (E) were measured. We investigated how time-course changes in follicular cell proliferation, estrogen receptor beta (ERbeta), apoptosis, and FSH and E concentrations are connected with follicular growth and atresia. Apoptosis was found in the ova from Day 0 to Day 3. On Day 15, apoptosis occurred in some granulosa cell nuclei in some follicles, but BrdU uptake and the presence of cyclin D2 and ER beta could be observed in other granulosa cells. From Day 17, apoptosis increased in the follicular granulosa cells, and BrdU uptake and the presence of cyclin D2 and ERbeta were decreased. Follicular atresia continued, reaching a peak on Day 30. Serum FSH and E concentrations increased until Day 15, then markedly decreased after Day 17. The mechanism of apoptosis in the ova from Day 0 to 3 has not been clarified. However, the onset of follicular atresia was caused by apoptotic degeneration from Days 15 to 17. These results showed that the oocytes were selected by apoptosis at 2 points in the time-course of the maturation of the ovary.     

A comparative histologic study of thyroid follicular size and epithelium percentage in certain mammals

The size and epithelium percentage of mammalian thyroid follicles were studied by making camera lucida drawings of histologic sections on calibrated graph paper. The average horizontal dimension of 500 follicles per animal was calculated together with the percentage amount occupied by follicular epithelium. With a few exceptions, folicular size tends to increase with increasing body size, while epithelium percentage decreases.     

Role of integrins during fertilization in mammals

Fertilization includes sperm-oocyte recognition, adhesion, binding, fusion and egg activation. Integrin receptors, which are adhesion molecules, are expressed on sea urchin, mouse, hamster and human unfertilized oocytes. Potential sperm ligands have been identified. A role for integrins during fertilization is supported by inhibition of sperm-egg adhesion and/or fusion by means of anti-integrin monoclonal antibodies, Arg-Gly-Asp (RGD) or disintegrin-like peptides. In several cell-cell interactions, such as lymphocyte activation, viral fusion, bacterial infection or macrophage phagocytosis, integrins act as co-receptors after activation and, by clustering in a multimolecular complex, are able to transduce signals through cytoskeletal proteins and adaptor kinases. Experimental data suggest that they may act in a similar way during fertilization and may participate to initiation and/or propagation of the calcium signal via stimulation of phospholipase C gamma and inositol trisphosphate production.     

凝集素DBA和WGA的受体在生殖周期小鼠子宫内膜中的亲合细胞化学

目的：探讨凝集素DBA和WGA的受体在胚泡着床过程中的生物学作用。方法：取生殖周期不同阶段的小鼠子宫内膜组织，采用亲合细胞化学和图像分析方法，检测WGA和DBA的受体在子宫内膜中的分布和变化情况。结果：以上2种凝集素受体均存在于生殖周期不同阶段的小鼠子宫内膜，但2者的存在部位和数量有差异。WGA受体广泛存在于子宫内膜腔上皮和腺上皮的游离缘，以及孕期胚胎组织和蜕膜细胞表面及ECM，DBA受体仅见于子宫内膜或胚胎组织血管的内皮及其基膜。并且2种受体在孕早期，尤其是围植入期的水平均显著高于间情期和哺乳期的水平。结论：凝集素WGA和DBA的受体与小鼠胚泡植入过程相关。     

Gamma-tubulin during the differentiation of spermatozoa in various mammals and man

The distribution of gamma-tubulin as a marker of microtubule organizing centres (MTOC) was studied during spermiogenesis in rodents and in rabbit, monkey and man. A polyclonal antibody directed against human gamma-tubulin was used both for indirect immunofluorescence (IIF) and post-embedding immunogold procedures. In all species, gamma-tubulin was detected in the proximal and distal centrioles of round spermatids. In elongating spermatids, gamma-tubulin was predominantly found in the pericentriolar material (PCM) of both centrioles and particularly around the adjunct of the proximal centriole. At this level, some labelling was also associated with manchette microtubules, but other parts of the manchette and the nuclear ring were never labelled. We propose a role for distal centriole gamma-tubulin in axoneme nucleation and centriolar adjunct gamma-tubulin in manchette nucleation. The disappearance of gamma-tubulin in mature spermatozoa indicates that sperm aster nucleation should be dependent on oocyte gamma-tubulin. Remnants of gamma-tubulin in some human spermatozoa suggest that paternal gamma-tubulin also could contribute to sperm aster formation.      

Tracheal compression delays alveolar collapse during deep diving in marine mammals

Marine mammals have very compliant alveoli and stiff upper airways; an adaptation that allows air to move from the alveoli into the upper airways, during breath-hold diving. Alveolar collapse is thought occur between 30 and 100 m and studies that have attempted to estimate gas exchange at depth have used the simplifying assumption that gas exchange ceases abruptly at the alveolar collapse depth. Here we develop a mathematical model that uses compliance values for the alveoli and upper airspaces, estimated from the literature, to predict volumes of the respiratory system at depth. Any compressibility of the upper airways decreases the volume to contain alveolar air yielding lung collapse pressures 2x that calculated assuming an incompressible upper airway. A simple relationship with alveolar volume was used to predict relative pulmonary shunt at depth. The results from our model agree with empirical data on gas absorption at depth as well as the degree of tracheal compression in forced and free diving mammals.     

Lysosomal enzyme cytochemistry in acute leukaemia

A cytochemical study of the lysosomal enzyme beta-glucuronidase in 60 cases of acute leukaemia has shown a qualitative difference in the cytoplasmic distribution of the enzyme between blast cells of the lymphoid and myeloid cell series. This difference provides a useful additional method for cytochemical classification of cell type and is superior in this respect to the other lysosomal enzymes studied (aryl sulphatase and acid phosphatase). The beta-glucuronidase reaction is recommended in those cases of acute leukaemia in which the periodic acid-Schiff reaction is negative or equivocal.     

Neutrophil cytochemistry in bacterial infection.

A new cytochemical technique, sensitive to altered lysosomal membrane permeability of blood neutrophils, has been evaluated as a screening test for bacterial infection. This technique, for the lysosomal enzymes acid phosphatase and chloroacetate esterase, was compared with the neutrophil alkaline phosphatase and nitroblue tetrazolium tests. The mean score for each method was significantly higher in infected patients than in normal controls. There was, however, considerable overlap of individual scores between infected patients and ill, but uninfected, patients. This overlap limits the diagnostic value of existing cytochemical screening methods.