Evolution and development of the vertebrate skull: The role of pattern formation

The vertebrate skull is anatomically complex and phylogenetically diverse; it presents unique opportunities to examine the role of developmental processes in evolutionary change. Previous studies have largely examined phylogenetic trends in tissue composition or change in the timing of developmental events (heterochrony). Additional important insights may be gained if skull evolution and development are viewed from the standpoint of pattern formation. Contemporary models of pattern formation offer the possibility of linking developmental mechanisms of cranial morphogenesis from the level of genes, through cell biology, to adult form.     

Chitinase: a novel target for blocking parasite transmission?

In many species of blood-sucking arthropod, the internal tissues are covered by chitinous material that may hinder parasite invasion. To circumvent this potential barrier, therefore, parasites have developed mechanisms that involve the enzyme chitinase. In this review, Mohammed Shohobuddin and David C. Kaslow examine the relationship between chitinase and parasite transmission.     

Female control of paternity

Of the two components of sexual selection, female choice is much less obvious than male-male competition, and hence has always been considered to be of secondary importance. However, recent field observations and new theory have brought about a radical change of emphasis. It now appears that although a female's choice of who fathers her offspring often occurs in a subtle manner, it may be widespread and take place through a variety of behavioural and physiological mechanisms, including the manipulation of male behaviour and the selection of sperm within the female reproductive tract.     

Effect of bovine somatotropin on reproductive function in lactating dairy cows

Several recent experiments have reported that chronic treatment with bovine somatotropin (bST) increased the number of days open without affecting the services per conception. The physiological basis for these effects was examined. Eleven lactating Holstein cows received daily injections of bST (40 mg) and 10 received daily injections of vehicle. Treatment was initiated between 32 and 85 d post partum and continued for up to 180 d. Eight of 11 bST-treated cows experienced at least one period of extended ovarian acyclicity during treatment. Only 3 of 10 control cows did so (P = 0.05). Concentrations of progesterone during luteal phases were lower in bST-treated cows than in controls (P = 0.06). Baseline concentrations of LH were suppressed in bST-treated cows compared with those of controls (P < 0.04). Neither the pulse frequency of LH nor the expression of estrous behavior was affected by bST (P > 0.30). These results indicate that chronic administration of a high dose of bST can reduce reproduction performance by promoting ovarian acyclicity.     

Two kinds of thick filament in smooth muscle cells in the adductor of a clam, Chlamys nobilis

The ultrastructure of the opaque portion of the adductor muscle in the pecten Chlamys nobilis was investigated. The opaque portion was composed of smooth muscle cells that contained thin and thick filaments. The thick filaments were classified into two kinds, thinner and thicker, according to the statistical analysis of diameters. They were also classified as being shorter and longer, when isolated native filaments were examined. The thick filaments may consequently be classified into two kinds: thinner and shorter filaments, and thicker and longer ones. The thinner and shorter filaments were about 26.5 nm in diameter and 7.5 mum in length, and the thicker and longer ones were about 42.0 nm in diameter and 13.0 mum in length, respectively. A regular periodicity was apparent on the surface of the core after removal of myosin molecules from its surface. The periodicity seemed similar for the two kinds of thick filament.     

The osmoregulatory tissue around the afferent blood vessels of the coxal gills in the estuarine amphipods, Grandidierella japonica and Melita setiflagella

By electron microscopy of the coxal gills in two species of estuarine amphipod crustaceans, Grandidierella japonica and Melita satifragella, we found a patch-like, specialized tissue area which consisted of unique cells closely resembling the salt-excreting cells in the gill of the brine shrimp and so-called chloride cells in teleost gills. These cells were characterized by an abundance of mitochondria, two kinds of extensive networks of cytoplasmic tubules, well-developed lamellar infoldings of the basal cell membrane, sparse microvillous projections of the apical border, and numerous large vacuoles with several incomplete partitions. The large (60 nm in diameter) and the small (30 nm) cytoplasmic tubular networks were found in the basal and the apical portions of the cell, respectively. The large networks, which were both directly and indirectly (through the lamellar system) continuous with the basal cell membrane, were regarded as extensions of the cell membrane. Both the outer walls and the partition walls of the vacuoles were reinforced with a parallel array of microtubules. The results suggest that this unique tissue plays an important role in the active transport of electrolytes to maintain a constant osmotic pressure of the hemolymph under widely fluctuating salinities of the estuarine environments.     

Characterization of seminal plasma proteins and sperm proteins in ejaculates from normospermic bulls and bulls with thermally-induced testicular degeneration

Semen was collected from 5 mature beef bulls by electroejaculation before, during, and after 20 days of scrotal insulation. Thermally-induced testicular degeneration was irreversible in 3 of the bulls. Analysis of sperm and seminal plasma polypeptides revealed that 15 to 30 sperm polypeptides and 25 to 30 seminal plasma polypeptides were indistinguishable between bulls prior to the insulation treatment. Changes in the sperm polypeptides pattern appeared as early as 2 days after the insulation treatment and persisted for at least 11 months in 2 of the bulls. In the spermatozoa, there was a detectable loss of 31, 34, 49 and 58 kDa polypeptides and an appearance of 6 to 8 new major polypeptides, ranging from 32 to 83 kDa. The 83 kDa polypeptide was most prominent in the 2 bulls that regained normal sperm motility and morphology following the insulation period. The post-insulation appearance of a seminal plasma polypeptide (circa 60 kDa) was also identified in these 2 bulls. Seminal plasma polypeptides remained qualitatively unaltered by the insulation treatment in the 3 bulls with irreversible testicular degeneration.     

Interrelationships among fluorometric analyses of spermatozoal function, classical semen quality parameters and the fertility of frozen-thawed bovine spermatozoa

Cryopreserved spermatozoa from 8 bulls were used to examine the interrelationships among flow cytometric spermatozoal quality assessments and classical semen quality parameters and nonreturn rate estimates of fertility. The integrity of the sperm cell membrane and the functional capacity of the mitochondria were quantified by flow cytometry after concurrent staining with carboxydimethylfluorescein diacetate (CDMFDA), propidium iodide (PI), and rhodamine 123 (R123). For each sample a total of 10,000 stained spermatozoa were simultaneously quantified for the intensity of their green and red fluorescence. Three straws from each bull were each examined initially and following incubation at 37 degrees C for 3 hours to assess the rate of senescence. The proportion of spermatozoa retaining membrane integrity and having functional mitochondria, as determined by CDMFDA and R123 staining, were compared with classical semen quality assessments (sperm motility, acrosomal status, cellular and head morphology, presence of vacuoles/craters and cytoplasmic droplets) and with fertility (nonreturn to estrus rates). For individual ejaculates nonreturn rates, the range was from 61.8 to 78.8%, whereas the cumulative rates of several ejaculates for each bull ranged from 71.3 to 83.5%. The proportion of spermatozoa with functional membranes and mitochondria were positively correlated with the percentage of spermatozoa with normal morphology (r=0.82; P=0.01) and motility after 4 hours of incubation (r=0.78; P=0.02), but not with the estimates of fertility. The actual number of spermatozoa per straw staining with CDMFDA and R123 after 4 hours of incubation at 37 degrees C was correlated with the percentage of spermatozoa with normal morphology (r=0.73; P=0.04). Multiple regression equations indicated that combinations of semen quality measurements could be useful in estimating fertilizing potential.     

The accuracy of enzyme-linked immunosorbent assay and latex agglutination progesterone test for the validation of estrus and early pregnancy diagnosis in dairy cattle

The accuracy of the enzyme-linked immunosorbent assay (ELISA) and the latex agglutination (LA) on-farm progesterone kit for detecting estrus and diagnosing early pregnancy was investigated in this study. Italian Friesian dairy cows (n=82) from 6 dairy herds were used for the collection of foremilk samples at the time of breeding and at 19, 21, and 23 days post insemination. Pregnancy status was ascertained by uterine palpation per rectum 40 to 60 days post insemination. Progesterone levels were affected by herd, percentage of milk fat, and the day of testing x diagnosis interaction. Validation of estrus by qualitative on-farm tests was 74.6% (LA) and 100.0% (ELISA) accurate using 0.5 ng/ml of progesterone as the RIA estimate for estrus. The accuracy rate for early pregnancy diagnosis by RIA was 68.4 to 83.8% for day 19 and day 21, respectively, while the detection rate for nonpregnancy was 84.6 to 100% on day 19 and day 21, respectively, as compared with uterine palpation per rectum. The average accuracy rate for early pregnancy diagnosis ranged from 84.7 to 92.3% for the LA and ELISA tests, respectively; the nonpregnancy rate was correctly predicted 93.9% to 68.2% for the LA and ELISA tests, respectively.     

A simplified laparoscopy technique for repeated ovarian observation in the water buffalo (Bubalus bubalis)

A simplified technique of laparoscopy was developed for ovarian observation in the riverine buffalo, through a right paralumbar incision. The technique differed from previously described ones in that it involved only a single puncture and required no abdominal insufflation. A Hopkins 0 degrees forward viewing endoscope (5.5 mm x 500 mm) in combination with an endoscope sheath having a built-in instrument channel, and a long flexible forceps (630 mm) were used. Of the 23 observation attempts on 13 buffalo, 21 successful observations were conducted. Laparoscopies were performed using a combination of Xylazine, local infiltration and epidural anesthesia in a standing position. Six repeated observations were made within a 21-day period on 1 buffalo, with no postoperative complications. Observation of both left and right ovaries was possible through the same puncture. The technique was useful in buffalo to confirm ovarian structures which could not be determined with certainty through palpation per rectum. Our results suggest that the single puncture laparoscopy technique can be safely used for repeated ovarian examination in the water buffalo.