OBSERVATIONS ON THE BASEMENT MEMBRANES IN RAT KIDNEY

Basement membranes in the kidney are made up of a homogeneous matrix. In argyria, silver passes from the blood in the ionic form and diffuses into the kidney basement membranes in which it is precipitated. X-ray diffraction studies of "silver-stained" rat kidneys show that most of the silver in the kidneys is combined with some form of sulfur. Histochemical staining for sulfhydryls and disulfides demonstrates the presence of these groups in basement membranes. It appears that silver ions combine with either or both the sulfhydryl or disulfide groups in the basement membranes and also in mitochondria (when the silver diffuses into a cell).     

OBSERVATIONS ON THE MORPHOLOGY AND PHYSIOLOGY OF MARSILEA SPERM

The multiciliated sperm of the water fern Marsilea vestita was examined with a view to establishing its suitability as an experimental subject. Time-course experiments revealed spermatid development to be temperature dependent. Sterile techniques were devised for observation of sperm on both a population and an individual basis. Sperm discharge, active and senescing sperm were examined by phase-contrast microscopy. A regular pattern of senescence was ascertained. This included vacuolation of the cytoplasmic vesicle, loss of motility, and ultimate loss of the helical structure of the sperm coil. Sperm life spans were recorded using motility and O₂ uptake as criteria. Sperm populations are active 3–3½ hr at ambient temperature (22–25 C). Individual sperm are active less than 1 hr. Sperm suspensions show a decline in O₂ uptake which parallels the loss of motility. Various constituents affecting the life span were investigated. A twofold prolongation of the sperm life span occurred in the presence of 0.1 m sucrose. An ultrastructural examination of the mature sperm was made to aid in assessing its metabolic potential. The sperm shows little ultrastructural differentiation. The cytoplasmic vesicle is predominantly composed of starch-containing plastids. The main structural components of the sperm coil are a continuous mitochondrial band, an elongate nucleus, and a series of microtubules which separate the basal bodies from the nucleus and mitochondrion. A comparison of ultrastructural features common to Pteridium and Marsilea was made and factors affecting senescence discussed.     

OBSERVATIONS ON PURINE METABOLISM IN RAT BRAIN

Both de novo and preformed base or salvage pathways are simultaneously operative in the biosynthesis of purine nucleotides in rat brain per se. A preferential utilization of de novo precursors is demonstrated.     

SPERM THRUSTS AND THE PROBLEM OF PENETRATION

An equation of Lighthill's is used to calculate sperm thrusts. They have values in the range 5–350 pN, depending on species. The limitations of this approach are discussed and comparison is made with the measured thrust for human sperm. The effect of sperm thrusts of this magnitude on covalent bonds and reversible bonds is discussed. Sperm cannot break covalent bonds, but can reduce the lifetime of reversible bonds.
The structure and physical properties of the zona pellucida are examined in relation to sperm penetration. The evidence suggests that sperm cannot penetrate it solely by force. A model for sperm penetration is elaborated in which the conjunctive application of thrust and a soluble enzyme leads to strain-induced proteolysis and the formation of the penetration slit. The potential mechanism of the zona block is discussed, as is the site of the acrosome reaction. The effects of other mechanical inputs into fertilization such as stirring and swimming are examined briefly. Evidence suggests that sperm penetration of the cumulus oophorus and cervical mucus is mechanical, but that in the case of cervical mucus, it is affected by changes in the physical properties of the mucus.     

OBSERVATIONS ON THE BIOSYNTHESIS OF RAT BRAIN CERAMIDE AND CEREBROSIDE IN VIVO

Abstract— The incorporation in vivo of l -[¹⁴C]serine into ceramide and cerebroside of young rat brain has been studied. Acid hydrolysis of labelled ceramide and galactosyl-ceramide followed by selective partitioning of the resulting components indicated that 88 per cent of the radioactivity was present in the long-chain base portion. At early time points (10 min, 20 min) the precursor was incorporated into ceramide and to a lesser degree into glucosyl-ceramide. During time intervals of 5 and 10 h, the specific activity values (d.p.m./μmol) for ceramide and glucosyl-ceramide decreased, while values for galactosyl-ceramide, containing either unsubstituted fatty acids (NFA) or α-hydroxy fatty acids (HFA), increased 50 and 30 per cent, respectively. Analysis of labelled ceramide at all time points studied (10 min-10 h) indicated that l -[¹⁴C]serine was incorporated onto the NFA type. This observation suggests that HFA-ceramide may not be the physiological precursor of HFA-galactosyl-ceramide. In this context, the postulated precursor roles of both ceramide and psychosine in the biosynthesis of brain cerebrosides are discussed.     

日本血吸虫尾蚴钻穿宿主皮肤的方式

本文报道了日本血吸虫尾蚴钻穿宿主皮肤的全过程和早期童虫在8种动物皮肤中动态分布的结果。阐明了血吸虫尾蚴钻穿宿主皮肤是依靠其体内头腺及/或钻腺分泌物的酶促作用、头器伸缩的探查作用及全身肌肉运动的机械作用而协同完成的。指出了尾蚴入侵皮肤界面和童虫在皮肤内移行常以倾斜角度前进,并非完全呈垂直方向或沿毛囊皮脂腺的通道。观察到童虫钻破皮肤血管壁进入血管腔的情景,这有力地提供了血吸虫童虫从皮肤进入血液循环系统的直接证据。     

SPERM PENETRATION AND THE FORMATION OF A FERTILIZATION CONE IN THE COMMON CARP EGG*

Sperm penetration and the formation of a fertilization cone in the micropylar canal of the egg of the common carp were examined by electron microscopy. The overwhelming majority of inseminated eggs fixed without immersion in fresh water showed that the first spermatozoon had penetrated into the ooplasm before the cortical reaction had occurred, and in many cases had formed a fertilization cone to plug the micropylar canal. At this stage the sperm head was usually located at the base of the cone, and the tail part did not participate in the formation of the cone. Inseminated eggs fixed soon after immersion in fresh water showed that the elevation of the fertilization membrane and the simultaneous recession of the fertilization cone often permitted the penetration of a few supernumerary spermatozoa into the perivitelline space near the micropylar canal, but polyspermic fertilization was never observed. The mechanism of the block to polyspermy in the egg of the common carp is discussed in connection with the fertilization cone.     

尼罗罗非鱼成熟卵结构及精子入卵早期的电镜观察

用扫描电镜观察尼罗罗非鱼(Tilopia nilotica)成熟卵卵膜孔结构和精子入卵的早期情况,用透射电镜观察成熟卵皮质,可见卵膜孔包括前庭和精孔管两部分,前庭壁及壳膜外表面上有许多小孔洞,精孔管壁呈阶梯状。卵膜孔下的卵皮质是一凹陷区,这一区域存在着皮质小泡。本实验见到5种形态的皮质小泡,其中大的皮质小泡靠近质膜。     

ELECTRON MICROSCOPIC OBSERVATIONS ON THE LARGE SUBUNIT OF THE RAT LIVER RIBOSOME

Active large subunits obtained by urea treatment of rat liver ribosomes, 59S, were compared with large subunits in intact ribosomes and with the 50S subunits obtained by EDTA treatment. For electron microscopy the specimens were negatively stained or shadow cast. The negatively stained 59S subunits had a slightly ovoidal form; their average dimensions, 244 ± 17 x 207 ± 18 A, were very close to the dimensions of the large subunits in intact ribosomes, and lay between the theoretical dimensions for anhydrous and fully hydrated particles that were calculated from the physical properties of the subunits in solution. The shadow-cast preparations showed particles of similar shape. The 50S subunits, which had lost their 5S RNA, were shadow cast at the same time. They appeared to be more spread out than the 59S subunits and had threadlike extensions. In the positively stained regions of uranyl oxalate-stained preparations the 50S particles varied greatly in shape and size, with average dimensions of 330 ± 21 x 276 ± 33 A, and showed threadlike extensions like those of the shadow-cast particles. For 50S particles in solution the frictional drag of these extensions probably accounts for their low sedimentation coefficient.     

OBSERVATIONS ON PENETRATION OF LINDEN BRANCHES BY STYLETS OF THE APHID LONGISTIGMA CARYAE

Penetration of the bark of Tilia americana L., the linden tree, by Longistigma caryae (Harr.) is mainly intracellular. Like other aphids, L. caryae secretes a saliva sheath which encloses the path of the stylets, beginning with an external collar of sheath material on the surface of the periderm. Stylet sheaths within the bark gave positive reactions for callose, suggesting that, in reaction to wounding, punctured parenchyma cells secrete callose which diffuses throughout the stylet sheaths. Other, more conspicuous effects of wounding included: proliferation and enlargement of cells of the cortex and dilated rays bordering some stylet sheaths, formation of tylosoids in punctured sieve elements, deposition of massive amounts of callose in penetrated sieve elements and in sieve elements bordering penetrated cells, and stimulation of cambial activity and xylem differentiation. Stylet tips located in living sieve elements projected beyond their sheaths which terminated outside the sieve-element walls. It is suggested that such sieve elements can be considered to be functional. None of the living sieve elements containing stylet tips showed any signs of injury which could be attributed to the presence of the stylets. Stylet tips of feeding aphids were found in living sieve elements of both 1965 and 1966 phloem increments clearly indicating that L. caryae can feed on linden sieve elements more than 1 year of age.     

奶牛精子尾部主段外周致密纤维的电子显微镜观察

奶牛精子尾部主段的中央结构为轴丝。在轴丝的外方有外周致密纤维。外周致密纤维由中段延伸而来。进入主段后,9条外周致密纤维逐一终止。最早终止的是第8条纤维。随后的终止顺序是第3、7、4、2、6、5、9、1条。因此,9条外周致密纤维中,最长的是第1条纤维,最短的是第8条纤维。9条纤维按长短顺序排列依次是第1、9、5、6、2、4、7、3、8条。根据外周致密纤维数量的多寡,可以将主段分为10个区域。从近中段端至近末段端,这10个区域依次是9条、8条、7条、6条、5条、4条、3条、2条、1条、0条纤维区域。外周致密纤维的外方有一纤维鞘。纤维鞘的背侧纵柱和腹侧纵柱分别向内伸出一个嵴。在主段的0条纤维区域,纤维鞘直接位于轴丝之外。在纤维鞘的外方还有精子的细胞质膜。     

金鱼精子入卵过程的扫描电镜观察

本文采用扫描电镜观察了金鱼(Carassius auratus)卵壳膜(chorion)表面结构和精子入卵过程。在壳膜的卵膜孔(micropyle)区有5—10条沟和嵴。位于精孔管下面,卵的质膜为一束较长的微绒毛组成的精子穿入部(sperm entry site)。授精5s,精子头的顶部已附着于精子穿入部,随即两者的质膜发生融合,而围于精子头部四周的微绒毛迅速伸长形成一受精锥,它不断将精子头部包裹。授精110s,精子的头部和颈部已完全进入卵内,受精锥本身也渐趋消失,但精子尾部仍平躺于卵的表面。皮层小泡是在授精30s后才开始破裂并释放其内含物,导致卵子表面呈蜂窝状,并在无膜内表面附着了大量球状物。     

SOME OBSERVATIONS ON THE SITATUNGA IN KENYA

A 16-month study was made of sitatunga in a swamp in western Kenya, with particular reference to distribution within the habitat, daily activity, and food preferences. Absolute figures for density could not be obtained because of observational difficulties, but there was a minimum of 7.3 animals/linear km of swamp, or c. 55/km². The sitatunga preferred areas of swamp adjacent to patches of gallery forest, and areas where there was deep water and a dense growth of tall reeds. They were most active during the first five and last two hours of daylight, and at night. Much of this time was spent feeding. Feeding behaviour and food preferences were studied. The sitatunga usually moved along well-marked tracks through the swamp vegetation; some of these led to beds of flattened plants, raised above water level, which were probably used for resting and for breeding. The latter took place in most months of the year, with a possible peak in November. Calves remained hidden for some weeks after birth. Group size and structure were examined; most sightings were of single animals or groups of two. A majority of these two groupings were composed of adult females. The proportion of immature animals seen indicated a healthy population. Courtship behaviour was observed 18 times and mating once.     

SOME OBSERVATIONS ON THE FINE STRUCTURE OF THE LUTEIN CELLS OF X-IRRADIATED RAT OVARY

The ovaries of 10- to 13-week-old rats were exteriorized and irradiated with sterilizing doses of X-rays. Following treatment, the animals entered a phase of constant vaginal cornification. Animals were killed 8 to 12 wk after the onset of this phase, and their ovaries were prepared for electron microscopy. Tissue was fixed in glutaraldehyde, postfixed in osmium tetroxide (Millonig's, phosphate-buffered), and embedded in Epon. Lutein cells from these ovaries were compared with those from sham-irradiated controls. The cytoplasm of lutein cells from experimental animals was characterized by an increase in the amount of agranular endoplasmic reticulum and by an increase in the number of mitochondria. These mitochondria are more variable in external form and often possess increased numbers of villiform cristae. Other features noted were a decrease in the amount of cytoplasmic lipid granules and an increase in cell size and surface irregularity. The significance of the morphological findings is discussed in relation to ovarian hormone production in animals sterilized by X-irradiation.     

KILLER WHALE PREDATION ON SPERM WHALES: OBSERVATIONS AND IMPLICATIONS

In October 1997 we observed a herd of approximately 35 killer whales ( Orcinus orca ) attack a pod of nine sperm whales ( Physeter macrocephalus ) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a "wound and withdraw" strategy. Adult male killer whales stood by until the very end when one charged in and quickly killed a seriously wounded sperm whale that had been separated from the group. The sperm whales appeared largely helpless: their main defensive behavior was the formation of a rosette ("marguerite"-heads together, tails out). When the killer whales were successful in pulling an individual out of the rosette, one or two sperm whales exposed themselves to increased attack by leaving the rosette, flanking the isolated individual, and leading it back into the formation. Despite these efforts, one sperm whale was killed and eaten and the rest were seriously, perhaps mortally, wounded. We also present details of two other encounters between sperm whales and killer whales that we observed. Although sperm whales, because of various behavioral and morphological adaptations, were previously thought to be immune to predation, our observations clearly establish their vulnerability to killer whales. We suggest that killer whale predation has potentially been an important, and underrated, selective factor in the evolution of sperm whale ecology, influencing perhaps the development of their complex social behavior and at-sea distribution patterns.     

SUCKLING BEHAVIOR IN SPERM WHALE CALVES: OBSERVATIONS AND HYPOTHESES

This study is the first to describe quantitatively the apparent suckling behavior of sperm whale, Physeter macrocephalus (Linnaeus, 1758), calves using observations from both above and below the surface. Peduncle dives are short (mean 14 s) dives made by sperm whale calves beside the peduncle of an adult female, which were previously assumed to be indicative of suckling. Photo-identification and focal calf-follows were used to collect data during 177 peduncle dive bouts from 22 different calves (11 calves from the Caribbean Sea, 11 from the Sargasso Sea), one of which was followed on forty different days. We found that peduncle diving in sperm whale calves is laterally asymmetrical with a bias to the left side of the escorting adult (69.8% of peduncle dives) and that calves generally do not switch sides during a bout of peduncle dives (switches occurred in only 10.8% of bouts). Further subsurface observations gave insight into potential alternative functions of peduncle diving. These alternative hypotheses, including nasal suckling, and the existing supporting evidence for each are discussed. It is likely that peduncle diving is related to suckling but that the exact function of the dives and manner in which sperm whale calves ingest milk remains unclear.