Spermatozoa

A spermatozoon (alternate spelling spermatozoön or spermatozoa) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) The term spermatozoon comes from the Greek word σπέρμα (seed) and ζῷον (living being).

Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases,mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing a Y chromosomewill lead to a male (XY) offspring, while one bearing a X chromosome will lead to a female (XX) offspring—the ovum always providing a X chromosome. Sperm cells were first observed by Anton van Leeuwenhoek in 1677.

Humans

The human sperm cell is the reproductive cell in males and will only survive in warm environments, once leaving the body the sperm's survival is reduced and may cause the cell to die, decreasing the sperm quality. Sperm cells come in two types, "female" and "male". Sperm cells that give rise to female (XX) offspring after fertilization differ in that they carry an X-chromosome, while sperm cells that give rise to male (XY) offspring carry a Y-chromosome.

In male humans, sperm cells consists of a head 5 µm by 3 µm and a tail 41 µm long. The tail flagellates, which propels the sperm cell (at about 1–3 mm/minute in humans) by whipping in an elliptical cone. Semen has an alkaline nature, and they do not reach full motility (hypermotility) until they reach the vagina where the alkaline pH is neutralized by acidic vaginal fluids. This gradual process takes 20–30 minutes. In this time, fibrinogen from the seminal vesicles forms a clot, securing and protecting the sperm. Just as they become hypermotile, fibrinolysinfrom the prostate dissolves the clot, allowing the sperm to progress optimally.

The spermatozoon is characterized by a minimum of cytoplasm and the most densely packed DNA known in eukaryotes. Compared tomitotic chromosomes in somatic cells, sperm DNA is at least sixfold more highly condensed.

The specimen contributes with DNA/chromatin, a centriole and perhaps also an oocyte-activating factor (OAF). It may also contribute with paternal Messenger RNA (mRNA), also contributing to embryonic development.

Avoidance of immune system response

Glycoprotein molecules on the surface of ejaculated sperm cells are recognized by all human immune systems, and interpreted as a signal that the cell should not be rejected. The female immune system might otherwise attack sperm in the reproductive tract. The specific glycoproteins coating sperm cells are also utilized by some cancerous and bacterial cells, some parasitic worms, and HIV-infected white blood cells, thereby avoiding an immune response from the host organism.

The blood-testis barrier, maintained by the tight junctions between the Sertoli cells of the seminiferous tubules, prevents communication between the forming spermatozoa in the testis and the blood vessels (and immune cells circulating within them) within the interstitial space. This prevents them from eliciting an immune response. The blood-testis barrier is also important in preventing toxic substances from disrupting spermatogenesis.

Animals

Fertilization relies on spermatozoa for most sexually reproductive animals.

The fruit fly has the largest known spermatozoon relative to its size. Drosophila melanogaster produces sperm that can be up to 1.8 mm in size. The incredibly long tail is thought to block other sperm from entering the egg. The entire sperm, tail included, gets incorporated into the oocyte cytoplasm.

The wood mouse Apodemus slvaticus possesses spermatozoa with falciform morphology. What makes these gametocytes even more unique is the presence of an apical hook on the sperm head. This hook is used to attach to the hooks or to the flagella of other spermatozoa. Aggregation is caused by these attachments and mobile trains result. These trains provide improved motility in the female reproductive tract and are a means by which fertilization is promoted.

Sea urchins such as Arbacia punctulata—are ideal organisms to use in sperm research, they spawn large numbers of sperm into the sea, making them well-suited as model organisms for experiments.

Plants, algae and fungi

The gametophytes of bryophytes, ferns and some gymnosperms produce motile sperm cells, contrary to pollen grains employed in most gymnosperms and all angiosperms. This renders sexual reproduction in the absence of water impossible, since water is a necessary medium for sperm and egg to meet. Algae and lower plant sperm cells are often multi-flagellated (see image) and thus morphologically different from animal spermatozoa.

Some algae and fungi produce non-motile sperm cells, called spermatia. In higher plants and some algae and fungi, fertilization involves the migration of the sperm nucleus through a fertilization tube (e.g. pollen tube in higher plants) to reach the egg cell.

Spermatozoa production in mammals

Main article: Spermatogenesis

Spermatozoa are produced in the seminiferous tubules of the testes in a process called spermatogenesis. Round cells called spermatogonia divide and differentiate eventually to become spermatozoa. During copulation the cloaca or vagina gets inseminated, and then the spermatozoa move throughchemotaxis to the ovum inside a Fallopian tube or the uterus.

Spermatozoa activation

Main article: Acrosome reaction

Acrosome reaction on a Sea Urchin cell

Approaching the egg cell is a rather complex, multistep process of chemotaxis guided by different chemical substances/stimuli on individual levels of phylogeny. One of the most significant, common signaling character of the event is that a prototype of professional chemotaxis receptors, formyl peptide receptor (60.000 receptor/cell) as well as the activator ability of its ligand formyl Met-Leu-Phe have been demonstrated in the surface membrane even in the case of human sperms.Mammalian sperm cells become even more active when they approach an egg cell in a process called sperm activation. Sperm activation has been shown to be caused by calcium ionophores in vitro, progesteronereleased by nearby cumulus cells and binding to ZP3 of the zona pellucida. The cumulus cells are embedded in a gel-like substance made primarily of hyaluronic acid, and developed in the ovary with the egg and support it as it grows.

The initial change is called "hyperactivation", which causes a change in spermatozoa motility. They swim faster and their tail movements become more forceful and erratic.

A recent discovery links hyperactivation to a sudden influx of calcium ion into the tails. The whip-like tail (flagellum) of the sperm is studded with ion channels formed by proteins called CatSper. These channels are selective, allowing only calcium ion to pass. The opening of CatSper channels is responsible for the influx of calcium. The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment. Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization.

The second process in sperm activation is the acrosome reaction. This involves releasing the contents of the acrosome, which disperse, and the exposure of enzymes attached to the inner acrosomal membrane of the sperm. This occurs after the sperm first meets the egg. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg.

ZP3, one of the proteins that make up the zona pellucida, then binds to a partner molecule on the sperm. Enzymes on the inner acrosomal membrane digests the zona pellucida. After the sperm penetrates the zona pellucida, part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head diffuse into the egg.

Upon penetration, the oocyte is said to have become activated. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a zygote. In order to preventpolyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's zona pellucida renders them impenetrable shortly after the first sperm enters the egg.

Artificial storage

Spermatozoa can be stored in diluents such has the Illini Variable Temperature (IVT) diluent, which have been reported to be able to preserve high fertility of spermatozoa for over seven days. The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with CO₂.

Semen cryopreservation can be used for far longer storage durations. For human spermatozoa, the longest reported successful storage with this method is 21 years.

Sperma Abnormal 

Sperm morphology — the size and shape of sperm — is checked as part of a standard semen analysis for male infertility. The results of a sperm morphology exam indicate the percentage of sperm that appear normal when semen is viewed under a microscope.

Normal sperm have an oval head with a long tail. Abnormal sperm have head or tail defects — such as a large or misshapen head or a crooked or double tail. These defects may affect the ability of the sperm to reach and penetrate an egg.

However, having a large percentage of misshapen sperm isn't uncommon — and it won't necessarily keep a man from getting his partner pregnant. In fact, a sperm sample isn't considered out of the normal range unless most of the sperm are abnormally shaped. If pregnancy does occur, having abnormal sperm morphology doesn't increase the risk of having a child with birth defects.

In addition to sperm shape, a sperm analysis also checks the sperm's ability to move (motility) and the number of sperm present (sperm count). Motility problems and a low sperm count commonly occur along with abnormal sperm morphology, and can also affect male fertility.

If a semen analysis shows abnormal sperm morphology or other irregularities, a wait-and-see approach is generally tried first. Another semen analysis is usually done after four to six weeks to see whether sperm quality has improved on its own. If there are still large numbers of abnormal sperm or a low sperm count, tests may be necessary to look for an underlying problem.

In some cases, sperm problems are due to a permanent condition — such as a testicle abnormality present at birth — and can't be treated. In other cases, sperm quality improves when an underlying condition gets better. Some common causes of abnormal sperm that are temporary or may be reversed with treatment include:

• Enlargement of veins within the scrotum (varicocele)
• High fever
• Use of certain illegal drugs
• Infection

Even with abnormal sperm morphology, motility problems or a low sperm count, pregnancy may still be possible. However, pregnancy doesn't always occur right away. For some couples, it can take a year or more. If you and your partner aren't able to conceive through sexual intercourse, assisted reproductive technology such as in vitro fertilization may be an option.

Sputum

Sputum Abnormal

Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections.

The best sputum samples contain very little saliva, as this contaminates the sample with oral bacteria. This event is assessed by the clinical microbiologist by examining a Gram stain of the sputum. More than 25 squamous epithelial cells at low enlargement indicates salivary contamination.

When a sputum specimen is plated out, it is best to get the portion of the sample that most looks like pus onto the swab. If there is any blood in the sputum, this should also be on the swab.

Microbiological sputum samples are usually used to look for infections by Moraxella catarrhalis, Mycobacterium tuberculosis, Streptococcus pneumoniaeand Haemophilus influenzae. Other pathogens can also be found.

Purulent Sputum contains a lot of pus, composed of white blood cells, cellular debris, dead tissue, serous fluid and viscous liquid (mucus). Mostly, it's yellow in color, as well as green. That is always seen in cases of bronchiectasis, lung abscess, or advanced stage of bronchitis, acute upper respiratory tract infection (cold, laryngitis).

Sputum can be:

1. Bloody (Hemoptysis)
   1. blood-streaked sputum - inflammation of throat, bronchi; lung cancer;
   2. Pink sputum - sputum evenly mixed with blood, from alveoli, small bronchi;
   3. massive blood - cavitary tuberculosis of lung, lung abscess, bronchiectasis, infarction, embolism.
2. Rusty colored - usually caused by pneumococcal bacteria (in pneumonia)
3. Purulent - containing pus. The color can provide hints as to effective treatment in Chronic Bronchitis Patients
   1. a yellow-greenish (mucopurulent) color suggests that treatment with antibiotics can reduce symptoms. Green color is caused by Neutrophil Myeloperoxidase.
   2. a white, milky, or opaque (mucoid) appearance often means that antibiotics will be ineffective in treating symptoms. (This information may correlate with the presence of bacterial or viral infections, though current research does not support that generalization.)
4. Foamy white - may come from obstruction or even edema.
5. Frothy pink - pulmonary edema

Sputum Culture

A sputum culture is a test to detect and identify bacteria or fungi(plural of fungus) that are infecting the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the airways leading to the lungs. A sample of sputum is placed in a container with substances that promote the growth of bacteria or fungi. If no bacteria or fungi grow, the culture is negative. If organisms that can cause infection (pathogenic organisms) grow, the culture is positive. The type of bacterium or fungus will be identified with a microscope or by chemical tests.

If bacteria or fungi that can cause infection grow in the culture, other tests may be done to determine which antibiotic will be most effective in treating the infection. This is called susceptibility or sensitivity testing.

This test is done on a sample of sputum that is usually collected by coughing. For people who can't cough deeply enough to produce a sample, they can breathe in a mist solution to help them cough.

• Why It Is Done

A sputum culture is done to:

• Find and identify bacteria or fungi that are causing an infection (such as pneumonia or tuberculosis) of the lungs or the airways leading to the lungs. Symptoms of a lung infection may include difficulty breathing, pain when breathing, or a cough that produces bloody or greenish brown sputum.
• Identify the best antibiotic to treat the infection (sensitivity testing).
• Monitor treatment of an infection.

• How To Prepare

Do not use mouthwash before collecting a sputum sample because it may contain antibacterial substances that could affect your results.

If bronchoscopy will be used to collect your sputum sample, your doctor will tell you how soon before the test to stop eating and drinking. Follow the instructions exactly about when to stop eating and drinking, or your surgery may be canceled. If your doctor has instructed you to take your medicines on the day of surgery, please do so using only a sip of water.

Tell your doctor if you have recently taken any antibiotics.

• How It Is Done

Usually, the sputum sample is collected early in the morning before you eat or drink anything. In some cases (especially if you may have tuberculosis), three or more morning samples may be needed.

If you wear dentures, you will need to remove them before collecting a sputum sample. Then rinse your mouth with water, take a deep breath, and then cough deeply to produce a sample of sputum. The health professional collecting the sample may tap on your chest to help loosen the sputum in your lungs before you cough. If you still have trouble coughing up a sample, you may be asked to inhale an aerosol mist to help you cough. Some people may need bronchoscopy to collect a sputum sample. During bronchoscopy, a thin, lighted tube (bronchoscope) is inserted through your mouth or nose into the airways leading to your lungs. You will be given medicine that numbs your throat and nose so you do not feel discomfort from the bronchoscope. You may also be given a sedative to make you sleepy during the procedure. To collect the sputum sample, a salt solution may be washed into the airway and then suctioned into a container. A small, thin brush may be used to collect a sample.

A sputum sample can also be collected using suction. During this procedure, a soft, flexible tube (called a nasotracheal catheter) is inserted through the nose and down the throat. Suction is applied for up to 15 seconds to collect the sputum sample. This method of collecting a sputum sample is often used for people who are very sick or unconscious.

In rare cases, a sputum sample may need to be collected by inserting a needle through the neck into the windpipe (trachea). This is called a transtracheal aspiration. Before a transtracheal aspiration, a local anesthetic is injected into the site where the needle will be inserted. Oxygen may be used before and after a transtracheal aspiration to help with breathing. This method of collecting a sputum sample may be used for people who are very sick and in the hospital.

Once the sputum sample is collected, it will be placed in a container with substances (growth medium or culture medium) that promote the growth of infecting organisms (bacteria or fungi). Bacteria usually need 2 to 3 days to grow. Fungus often takes a week or longer to grow. The organism that causes tuberculosis may take 6 weeks to grow. Any bacteria or fungi that grow will be identified under a microscope or by chemical tests. Sensitivity testing, to determine the best antibiotic to use against the organism that grows, often takes 1 to 2 additional days.

• How It Feels

If you have discomfort when taking a deep breath or when coughing, obtaining a sputum sample may be uncomfortable. If you need to inhale the aerosol mist to produce a sputum sample, you will often feel a deep, uncontrollable urge to cough.

During bronchoscopy or collection of a sputum sample using a catheter, you may feel a strong urge to cough as the bronchoscope or catheter passes into the back of your throat. You may also feel as if you cannot breathe. Try to relax and breathe slowly while the bronchoscope or catheter is in place. If you are given medicine to numb your throat and nose, you may feel as if your tongue and throat are swollen and that you cannot swallow.

In rare cases, a transtracheal aspiration is used to collect a sputum sample. The doctor will inject a local anesthetic to keep you from feeling any pain when the needle is inserted into your trachea. When you are given the local anesthetic, you will feel sharp stinging or burning that lasts a few seconds. When the needle is inserted into the trachea, you will again feel a sharp pain for a few seconds, similar to having your blood drawn. The doctor may ask you to hold your breath during key moments of the procedure.

• Risks

Your throat may feel sore following bronchoscopy or collection of a sputum sample using a nasotracheal catheter.

If you have severe asthma or bronchitis, you may find it hard to breathe during collection of a sputum sample using a nasotracheal catheter.

In rare cases, a transtracheal aspiration may damage your voice box (larynx) or cause an infection, excessive bleeding, or air to leak from your windpipe (trachea) into the tissues of your neck.

Results

A sputum culture is a test to detect and identify bacteria or fungi that are infecting the lungs or breathing passages. Some types of bacteria or fungi grow quickly in a culture and some grow slowly. Test results may take from one day to several weeks, depending on the type of infection suspected. Some organisms (such asChlamydophila pneumoniae and mycoplasma) do not grow in a standard culture and need a special growth medium to be detected in a sputum culture.

Sputum culture

Normal:	Sputum that has passed through the mouth normally contains several types of harmless bacteria, including some types of strep (Streptococcus) and staph (Staphylococcus). The culture should not show any harmful bacteria or fungi. Normal culture results are negative.
Abnormal:	Harmful bacteria or fungi are present. The most common harmful bacteria in a sputum culture are those that can cause bronchitis, pneumonia, or tuberculosis. If harmful bacteria or fungi grow, the culture is positive.

If test results point to an infection, sensitivity testing may be done to determine the best antibiotic to kill the bacteria or fungus.

• What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Recent use of antibiotics, which may prevent the growth of bacteria or fungi in the culture.
• Contamination of the sputum sample.
• An inadequate sputum sample.
• Waiting too long to deliver the sample to the laboratory.
• Use of mouthwash before collecting a sputum sample.

What To Think About

• Organisms (such as bacteria or a fungus) may be identified by using special dyes on the sputum sample. This is called a Gram stain. A Gram stain can help a doctor:
  • Determine whether the sputum sample is adequate for culture. For example, a sputum sample that is not collected properly may not contain enough bacteria to warrant a culture, or the sample may be contaminated by other bacteria that are not infecting the lungs. If the sample is not adequate for culture, another sample can be obtained.
  • Make an initial diagnosis before the culture results are received. In some cases, Gram stain results can be available within 30 minutes, whereas culture results may not be available for one to several days. Information received from a Gram stain can help your doctor treat the infection earlier, rather than waiting for the culture results.
• Because sputum collected by coughing usually contains bacteria from your mouth, these culture results must be considered along with your symptoms, condition, and other test results, such as a chest X-ray.
• A culture that does not grow any bacteria or fungi may not rule out an infection. Factors such as the amount of sample collected, the age of the infection, the type of culture done, and previous use of antibiotics can prevent the growth of bacteria or fungi in the culture.
• A special growth medium is needed for some cultures, such as for those that can find infection by tuberculosis (TB) bacteria, mycoplasma, Chlamydophila pneumoniae, or fungus. TB bacteria and most types of fungi grow very slowly and may not show up in a culture for several weeks. So treatment for a suspected fungus or TB infection may begin before culture results are known.
• Sensitivity testing helps a doctor choose the best medicine to kill specific types of bacteria or fungi infecting a person. Differences in the genetic material (DNA) of bacteria or fungi may make them resistant to certain antibiotics. In such cases, those antibiotics can't kill all of the bacteria. When an effective antibiotic is chosen, you must complete the entire course to lower the chance that the bacteria will become resistant to the antibiotic. Stopping antibiotic treatment early kills only the most sensitive bacteria, while those that are more resistant can multiply and prolong the infection. Subsequent infections may also be harder to treat if caused by resistant bacteria.
• Bronchoscopy is often done if a serious or recurring lung infection is present, especially when other tests have not definitely determined the cause. For more information, see the topic Bronchoscopy.
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adapted from : http://www.webmd.com/lung/sputum-culture , google.com